kernel/fs/btrfs/inode.c, branch linux-rolling-stable

btrfs: fix transaction abort on file creation due to name hash collision

2026-03-19T15:15:28Z

commit 2d1ababdedd4ba38867c2500eb7f95af5ddeeef7 upstream. If we attempt to create several files with names that result in the same hash, we have to pack them in same dir item and that has a limit inherent to the leaf size. However if we reach that limit, we trigger a transaction abort and turns the filesystem into RO mode. This allows for a malicious user to disrupt a system, without the need to have administration privileges/capabilities. Reproducer: $ cat exploit-hash-collisions.sh #!/bin/bash DEV=/dev/sdi MNT=/mnt/sdi # Use smallest node size to make the test faster and require fewer file # names that result in hash collision. mkfs.btrfs -f --nodesize 4K $DEV mount $DEV $MNT # List of names that result in the same crc32c hash for btrfs. declare -a names=( 'foobar' '%a8tYkxfGMLWRGr55QSeQc4PBNH9PCLIvR6jZnkDtUUru1t@RouaUe_L:@xGkbO3nCwvLNYeK9vhE628gss:T$yZjZ5l-Nbd6CbC$M=hqE-ujhJICXyIxBvYrIU9-TDC' 'AQci3EUB%shMsg-N%frgU:02ByLs=IPJU0OpgiWit5nexSyxZDncY6WB:=zKZuk5Zy0DD$Ua78%MelgBuMqaHGyKsJUFf9s=UW80PcJmKctb46KveLSiUtNmqrMiL9-Y0I_l5Fnam04CGIg=8@U:Z' 'CvVqJpJzueKcuA$wqwePfyu7VxuWNN3ho$p0zi2H8QFYK$7YlEqOhhb%:hHgjhIjW5vnqWHKNP4' 'ET:vk@rFU4tsvMB0$C_p=xQHaYZjvoF%-BTc%wkFW8yaDAPcCYoR%x$FH5O:' 'HwTon%v7SGSP4FE08jBwwiu5aot2CFKXHTeEAa@38fUcNGOWvE@Mz6WBeDH_VooaZ6AgsXPkVGwy9l@@ZbNXabUU9csiWrrOp0MWUdfi$EZ3w9GkIqtz7I_eOsByOkBOO' 'Ij%2VlFGXSuPvxJGf5UWy6O@1svxGha%b@=%wjkq:CIgE6u7eJOjmQY5qTtxE2Rjbis9@us' 'KBkjG5%9R8K9sOG8UTnAYjxLNAvBmvV5vz3IiZaPmKuLYO03-6asI9lJ_j4@6Xo$KZicaLWJ3Pv8XEwVeUPMwbHYWwbx0pYvNlGMO9F:ZhHAwyctnGy%_eujl%WPd4U2BI7qooOSr85J-C2V$LfY' 'NcRfDfuUQ2=zP8K3CCF5dFcpfiOm6mwenShsAb_F%n6GAGC7fT2JFFn:c35X-3aYwoq7jNX5$ZJ6hI3wnZs$7KgGi7wjulffhHNUxAT0fRRLF39vJ@NvaEMxsMO' 'Oj42AQAEzRoTxa5OuSKIr=A_lwGMy132v4g3Pdq1GvUG9874YseIFQ6QU' 'Ono7avN5GjC:_6dBJ_' 'WHmN2gnmaN-9dVDy4aWo:yNGFzz8qsJyJhWEWcud7$QzN2D9R0efIWWEdu5kwWr73NZm4=@CoCDxrrZnRITr-kGtU_cfW2:%2_am' 'WiFnuTEhAG9FEC6zopQmj-A-$LDQ0T3WULz%ox3UZAPybSV6v1Z$b4L_XBi4M4BMBtJZpz93r9xafpB77r:lbwvitWRyo$odnAUYlYMmU4RvgnNd--e=I5hiEjGLETTtaScWlQp8mYsBovZwM2k' 'XKyH=OsOAF3p%uziGF_ZVr$ivrvhVgD@1u%5RtrV-gl_vqAwHkK@x7YwlxX3qT6WKKQ%PR56NrUBU2dOAOAdzr2=5nJuKPM-T-$ZpQfCL7phxQbUcb:BZOTPaFExc-qK-gDRCDW2' 'd3uUR6OFEwZr%ns1XH_@tbxA@cCPmbBRLdyh7p6V45H$P2$F%w0RqrD3M0g8aGvWpoTFMiBdOTJXjD:JF7=h9a_43xBywYAP%r$SPZi%zDg%ql-KvkdUCtF9OLaQlxmd' 'ePTpbnit%hyNm@WELlpKzNZYOzOTf8EQ$sEfkMy1VOfIUu3coyvIr13-Y7Sv5v-Ivax2Go_GQRFMU1b3362nktT9WOJf3SpT%z8sZmM3gvYQBDgmKI%%RM-G7hyrhgYflOw%z::ZRcv5O:lDCFm' 'evqk743Y@dvZAiG5J05L_ROFV@$2%rVWJ2%3nxV72-W7$e$-SK3tuSHA2mBt$qloC5jwNx33GmQUjD%akhBPu=VJ5g$xhlZiaFtTrjeeM5x7dt4cHpX0cZkmfImndYzGmvwQG:$euFYmXn$_2rA9mKZ' 'gkgUtnihWXsZQTEkrMAWIxir09k3t7jk_IK25t1:cy1XWN0GGqC%FrySdcmU7M8MuPO_ppkLw3=Dfr0UuBAL4%GFk2$Ma10V1jDRGJje%Xx9EV2ERaWKtjpwiZwh0gCSJsj5UL7CR8RtW5opCVFKGGy8Cky' 'hNgsG_8lNRik3PvphqPm0yEH3P%%fYG:kQLY=6O-61Wa6nrV_WVGR6TLB09vHOv%g4VQRP8Gzx7VXUY1qvZyS' 'isA7JVzN12xCxVPJZ_qoLm-pTBuhjjHMvV7o=F:EaClfYNyFGlsfw-Kf%uxdqW-kwk1sPl2vhbjyHU1A6$hz' 'kiJ_fgcdZFDiOptjgH5PN9-PSyLO4fbk_:u5_2tz35lV_iXiJ6cx7pwjTtKy-XGaQ5IefmpJ4N_ZqGsqCsKuqOOBgf9LkUdffHet@Wu' 'lvwtxyhE9:%Q3UxeHiViUyNzJsy:fm38pg_b6s25JvdhOAT=1s0$pG25x=LZ2rlHTszj=gN6M4zHZYr_qrB49i=pA--@WqWLIuX7o1S_SfS@2FSiUZN' 'rC24cw3UBDZ=5qJBUMs9e$=S4Y94ni%Z8639vnrGp=0Hv4z3dNFL0fBLmQ40=EYIY:Z=SLc@QLMSt2zsss2ZXrP7j4=' 'uwGl2s-fFrf@GqS=DQqq2I0LJSsOmM%xzTjS:lzXguE3wChdMoHYtLRKPvfaPOZF2fER@j53evbKa7R%A7r4%YEkD=kicJe@SFiGtXHbKe4gCgPAYbnVn' 'UG37U6KKua2bgc:IHzRs7BnB6FD:2Mt5Cc5NdlsW%$1tyvnfz7S27FvNkroXwAW:mBZLA1@qa9WnDbHCDmQmfPMC9z-Eq6QT0jhhPpqyymaD:R02ghwYo%yx7SAaaq-:x33LYpei$5g8DMl3C' 'y2vjek0FE1PDJC0qpfnN:x8k2wCFZ9xiUF2ege=JnP98R%wxjKkdfEiLWvQzmnW' '8-HCSgH5B%K7P8_jaVtQhBXpBk:pE-$P7ts58U0J@iR9YZntMPl7j$s62yAJO@_9eanFPS54b=UTw$94C-t=HLxT8n6o9P=QnIxq-f1=Ne2dvhe6WbjEQtc' 'YPPh:IFt2mtR6XWSmjHptXL_hbSYu8bMw-JP8@PNyaFkdNFsk$M=xfL6LDKCDM-mSyGA_2MBwZ8Dr4=R1D%7-mCaaKGxb990jzaagRktDTyp' '9hD2ApKa_t_7x-a@GCG28kY:7$M@5udI1myQ$x5udtggvagmCQcq9QXWRC5hoB0o-_zHQUqZI5rMcz_kbMgvN5jr63LeYA4Cj-c6F5Ugmx6DgVf@2Jqm%MafecpgooqreJ53P-QTS' ) # Now create files with all those names in the same parent directory. # It should not fail since a 4K leaf has enough space for them. for name in "${names[@]}"; do touch $MNT/$name done # Now add one more file name that causes a crc32c hash collision. # This should fail, but it should not turn the filesystem into RO mode # (which could be exploited by malicious users) due to a transaction # abort. touch $MNT/'W6tIm-VK2@BGC@IBfcgg6j_p:pxp_QUqtWpGD5Ok_GmijKOJJt' # Check that we are able to create another file, with a name that does not cause # a crc32c hash collision. echo -n "hello world" > $MNT/baz # Unmount and mount again, verify file baz exists and with the right content. umount $MNT mount $DEV $MNT echo "File baz content: $(cat $MNT/baz)" umount $MNT When running the reproducer: $ ./exploit-hash-collisions.sh (...) touch: cannot touch '/mnt/sdi/W6tIm-VK2@BGC@IBfcgg6j_p:pxp_QUqtWpGD5Ok_GmijKOJJt': Value too large for defined data type ./exploit-hash-collisions.sh: line 57: /mnt/sdi/baz: Read-only file system cat: /mnt/sdi/baz: No such file or directory File baz content: And the transaction abort stack trace in dmesg/syslog: $ dmesg (...) [758240.509761] ------------[ cut here ]------------ [758240.510668] BTRFS: Transaction aborted (error -75) [758240.511577] WARNING: fs/btrfs/inode.c:6854 at btrfs_create_new_inode+0x805/0xb50 [btrfs], CPU#6: touch/888644 [758240.513513] Modules linked in: btrfs dm_zero (...) [758240.523221] CPU: 6 UID: 0 PID: 888644 Comm: touch Tainted: G W 6.19.0-rc8-btrfs-next-225+ #1 PREEMPT(full) [758240.524621] Tainted: [W]=WARN [758240.525037] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [758240.526331] RIP: 0010:btrfs_create_new_inode+0x80b/0xb50 [btrfs] [758240.527093] Code: 0f 82 cf (...) [758240.529211] RSP: 0018:ffffce64418fbb48 EFLAGS: 00010292 [758240.529935] RAX: 00000000ffffffd3 RBX: 0000000000000000 RCX: 00000000ffffffb5 [758240.531040] RDX: 0000000d04f33e06 RSI: 00000000ffffffb5 RDI: ffffffffc0919dd0 [758240.531920] RBP: ffffce64418fbc10 R08: 0000000000000000 R09: 00000000ffffffb5 [758240.532928] R10: 0000000000000000 R11: ffff8e52c0000000 R12: ffff8e53eee7d0f0 [758240.533818] R13: ffff8e57f70932a0 R14: ffff8e5417629568 R15: 0000000000000000 [758240.534664] FS: 00007f1959a2a740(0000) GS:ffff8e5b27cae000(0000) knlGS:0000000000000000 [758240.535821] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [758240.536644] CR2: 00007f1959b10ce0 CR3: 000000012a2cc005 CR4: 0000000000370ef0 [758240.537517] Call Trace: [758240.537828] [758240.538099] btrfs_create_common+0xbf/0x140 [btrfs] [758240.538760] path_openat+0x111a/0x15b0 [758240.539252] do_filp_open+0xc2/0x170 [758240.539699] ? preempt_count_add+0x47/0xa0 [758240.540200] ? __virt_addr_valid+0xe4/0x1a0 [758240.540800] ? __check_object_size+0x1b3/0x230 [758240.541661] ? alloc_fd+0x118/0x180 [758240.542315] do_sys_openat2+0x70/0xd0 [758240.543012] __x64_sys_openat+0x50/0xa0 [758240.543723] do_syscall_64+0x50/0xf20 [758240.544462] entry_SYSCALL_64_after_hwframe+0x76/0x7e [758240.545397] RIP: 0033:0x7f1959abc687 [758240.546019] Code: 48 89 fa (...) [758240.548522] RSP: 002b:00007ffe16ff8690 EFLAGS: 00000202 ORIG_RAX: 0000000000000101 [758240.566278] RAX: ffffffffffffffda RBX: 00007f1959a2a740 RCX: 00007f1959abc687 [758240.567068] RDX: 0000000000000941 RSI: 00007ffe16ffa333 RDI: ffffffffffffff9c [758240.567860] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [758240.568707] R10: 00000000000001b6 R11: 0000000000000202 R12: 0000561eec7c4b90 [758240.569712] R13: 0000561eec7c311f R14: 00007ffe16ffa333 R15: 0000000000000000 [758240.570758] [758240.571040] ---[ end trace 0000000000000000 ]--- [758240.571681] BTRFS: error (device sdi state A) in btrfs_create_new_inode:6854: errno=-75 unknown [758240.572899] BTRFS info (device sdi state EA): forced readonly Fix this by checking for hash collision, and if the adding a new name is possible, early in btrfs_create_new_inode() before we do any tree updates, so that we don't need to abort the transaction if we cannot add the new name due to the leaf size limit. A test case for fstests will be sent soon. Fixes: caae78e03234 ("btrfs: move common inode creation code into btrfs_create_new_inode()") CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Boris Burkov Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

btrfs: print correct subvol num if active swapfile prevents deletion

2026-03-12T11:09:23Z

[ Upstream commit 1c7e9111f4e6d6d42bc47759c9af1ef91f03ac2c ] Fix the error message in btrfs_delete_subvolume() if we can't delete a subvolume because it has an active swapfile: we were printing the number of the parent rather than the target. Fixes: 60021bd754c6 ("btrfs: prevent subvol with swapfile from being deleted") Reviewed-by: Qu Wenruo Reviewed-by: Filipe Manana Signed-off-by: Mark Harmstone Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin

Merge tag 'for-6.19-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

2026-01-18T03:29:32Z

Pull btrfs fixes from David Sterba: - with large folios in use, fix partial incorrect update of a reflinked range - fix potential deadlock in iget when lookup fails and eviction is needed - in send, validate inline extent type while detecting file holes - fix memory leak after an error when creating a space info - remove zone statistics from sysfs again, the output size limitations make it unusable, we'll do it in another way in another release - test fixes: - return proper error codes from block remapping tests - fix tree root leaks in qgroup tests after errors * tag 'for-6.19-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: remove zoned statistics from sysfs btrfs: fix memory leaks in create_space_info() error paths btrfs: invalidate pages instead of truncate after reflinking btrfs: update the Kconfig string for CONFIG_BTRFS_EXPERIMENTAL btrfs: send: check for inline extents in range_is_hole_in_parent() btrfs: tests: fix return 0 on rmap test failure btrfs: tests: fix root tree leak in btrfs_test_qgroups() btrfs: release path before iget_failed() in btrfs_read_locked_inode()

Merge tag 'for-6.19-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

2026-01-09T17:02:38Z

Pull btrfs fixes from David Sterba: - fix potential NULL pointer dereference when replaying tree log after an error - release path before initializing extent tree to avoid potential deadlock when allocating new inode - on filesystems with block size > page size - fix potential read out of bounds during encoded read of an inline extent - only enforce free space tree if v1 cache is required - print correct tree id in error message * tag 'for-6.19-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: show correct warning if can't read data reloc tree btrfs: fix NULL pointer dereference in do_abort_log_replay() btrfs: force free space tree for bs > ps cases btrfs: only enforce free space tree if v1 cache is required for bs < ps cases btrfs: release path before initializing extent tree in btrfs_read_locked_inode() btrfs: avoid access-beyond-folio for bs > ps encoded writes

btrfs: release path before iget_failed() in btrfs_read_locked_inode()

2026-01-09T16:41:41Z

In btrfs_read_locked_inode() if we fail to lookup the inode, we jump to the 'out' label with a path that has a read locked leaf and then we call iget_failed(). This can result in a ABBA deadlock, since iget_failed() triggers inode eviction and that causes the release of the delayed inode, which must lock the delayed inode's mutex, and a task updating a delayed inode starts by taking the node's mutex and then modifying the inode's subvolume btree. Syzbot reported the following lockdep splat for this: ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ btrfs-cleaner/8725 is trying to acquire lock: ffff0000d6826a48 (&delayed_node->mutex){+.+.}-{4:4}, at: __btrfs_release_delayed_node+0xa0/0x9b0 fs/btrfs/delayed-inode.c:290 but task is already holding lock: ffff0000dbeba878 (btrfs-tree-00){++++}-{4:4}, at: btrfs_tree_read_lock_nested+0x44/0x2ec fs/btrfs/locking.c:145 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (btrfs-tree-00){++++}-{4:4}: __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x198/0x39c kernel/locking/lockdep.c:5889 up_read+0x24/0x3c kernel/locking/rwsem.c:1632 btrfs_tree_read_unlock+0xdc/0x298 fs/btrfs/locking.c:169 btrfs_tree_unlock_rw fs/btrfs/locking.h:218 [inline] btrfs_search_slot+0xa6c/0x223c fs/btrfs/ctree.c:2133 btrfs_lookup_inode+0xd8/0x38c fs/btrfs/inode-item.c:395 __btrfs_update_delayed_inode+0x124/0xed0 fs/btrfs/delayed-inode.c:1032 btrfs_update_delayed_inode fs/btrfs/delayed-inode.c:1118 [inline] __btrfs_commit_inode_delayed_items+0x15f8/0x1748 fs/btrfs/delayed-inode.c:1141 __btrfs_run_delayed_items+0x1ac/0x514 fs/btrfs/delayed-inode.c:1176 btrfs_run_delayed_items_nr+0x28/0x38 fs/btrfs/delayed-inode.c:1219 flush_space+0x26c/0xb68 fs/btrfs/space-info.c:828 do_async_reclaim_metadata_space+0x110/0x364 fs/btrfs/space-info.c:1158 btrfs_async_reclaim_metadata_space+0x90/0xd8 fs/btrfs/space-info.c:1226 process_one_work+0x7e8/0x155c kernel/workqueue.c:3263 process_scheduled_works kernel/workqueue.c:3346 [inline] worker_thread+0x958/0xed8 kernel/workqueue.c:3427 kthread+0x5fc/0x75c kernel/kthread.c:463 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 -> #0 (&delayed_node->mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598 __mutex_lock kernel/locking/mutex.c:760 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812 __btrfs_release_delayed_node+0xa0/0x9b0 fs/btrfs/delayed-inode.c:290 btrfs_release_delayed_node fs/btrfs/delayed-inode.c:315 [inline] btrfs_remove_delayed_node+0x68/0x84 fs/btrfs/delayed-inode.c:1326 btrfs_evict_inode+0x578/0xe28 fs/btrfs/inode.c:5587 evict+0x414/0x928 fs/inode.c:810 iput_final fs/inode.c:1914 [inline] iput+0x95c/0xad4 fs/inode.c:1966 iget_failed+0xec/0x134 fs/bad_inode.c:248 btrfs_read_locked_inode+0xe1c/0x1234 fs/btrfs/inode.c:4101 btrfs_iget+0x1b0/0x264 fs/btrfs/inode.c:5837 btrfs_run_defrag_inode fs/btrfs/defrag.c:237 [inline] btrfs_run_defrag_inodes+0x520/0xdc4 fs/btrfs/defrag.c:309 cleaner_kthread+0x21c/0x418 fs/btrfs/disk-io.c:1516 kthread+0x5fc/0x75c kernel/kthread.c:463 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(btrfs-tree-00); lock(&delayed_node->mutex); lock(btrfs-tree-00); lock(&delayed_node->mutex); *** DEADLOCK *** 1 lock held by btrfs-cleaner/8725: #0: ffff0000dbeba878 (btrfs-tree-00){++++}-{4:4}, at: btrfs_tree_read_lock_nested+0x44/0x2ec fs/btrfs/locking.c:145 stack backtrace: CPU: 0 UID: 0 PID: 8725 Comm: btrfs-cleaner Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2043 check_noncircular+0x154/0x174 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common+0x1d0/0x2678 kernel/locking/mutex.c:598 __mutex_lock kernel/locking/mutex.c:760 [inline] mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:812 __btrfs_release_delayed_node+0xa0/0x9b0 fs/btrfs/delayed-inode.c:290 btrfs_release_delayed_node fs/btrfs/delayed-inode.c:315 [inline] btrfs_remove_delayed_node+0x68/0x84 fs/btrfs/delayed-inode.c:1326 btrfs_evict_inode+0x578/0xe28 fs/btrfs/inode.c:5587 evict+0x414/0x928 fs/inode.c:810 iput_final fs/inode.c:1914 [inline] iput+0x95c/0xad4 fs/inode.c:1966 iget_failed+0xec/0x134 fs/bad_inode.c:248 btrfs_read_locked_inode+0xe1c/0x1234 fs/btrfs/inode.c:4101 btrfs_iget+0x1b0/0x264 fs/btrfs/inode.c:5837 btrfs_run_defrag_inode fs/btrfs/defrag.c:237 [inline] btrfs_run_defrag_inodes+0x520/0xdc4 fs/btrfs/defrag.c:309 cleaner_kthread+0x21c/0x418 fs/btrfs/disk-io.c:1516 kthread+0x5fc/0x75c kernel/kthread.c:463 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 Fix this by releasing the path before calling iget_failed(). Reported-by: syzbot+c1c6edb02bea1da754d8@syzkaller.appspotmail.com Link: https://lore.kernel.org/linux-btrfs/694530c2.a70a0220.207337.010d.GAE@google.com/ Fixes: 69673992b1ae ("btrfs: push cleanup into btrfs_read_locked_inode()") Reviewed-by: Boris Burkov Signed-off-by: Filipe Manana Signed-off-by: David Sterba

btrfs: release path before initializing extent tree in btrfs_read_locked_inode()

2026-01-06T00:22:59Z

In btrfs_read_locked_inode() we are calling btrfs_init_file_extent_tree() while holding a path with a read locked leaf from a subvolume tree, and btrfs_init_file_extent_tree() may do a GFP_KERNEL allocation, which can trigger reclaim. This can create a circular lock dependency which lockdep warns about with the following splat: [6.1433] ====================================================== [6.1574] WARNING: possible circular locking dependency detected [6.1583] 6.18.0+ #4 Tainted: G U [6.1591] ------------------------------------------------------ [6.1599] kswapd0/117 is trying to acquire lock: [6.1606] ffff8d9b6333c5b8 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1625] but task is already holding lock: [6.1633] ffffffffa4ab8ce0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x195/0xc60 [6.1646] which lock already depends on the new lock. [6.1657] the existing dependency chain (in reverse order) is: [6.1667] -> #2 (fs_reclaim){+.+.}-{0:0}: [6.1677] fs_reclaim_acquire+0x9d/0xd0 [6.1685] __kmalloc_cache_noprof+0x59/0x750 [6.1694] btrfs_init_file_extent_tree+0x90/0x100 [6.1702] btrfs_read_locked_inode+0xc3/0x6b0 [6.1710] btrfs_iget+0xbb/0xf0 [6.1716] btrfs_lookup_dentry+0x3c5/0x8e0 [6.1724] btrfs_lookup+0x12/0x30 [6.1731] lookup_open.isra.0+0x1aa/0x6a0 [6.1739] path_openat+0x5f7/0xc60 [6.1746] do_filp_open+0xd6/0x180 [6.1753] do_sys_openat2+0x8b/0xe0 [6.1760] __x64_sys_openat+0x54/0xa0 [6.1768] do_syscall_64+0x97/0x3e0 [6.1776] entry_SYSCALL_64_after_hwframe+0x76/0x7e [6.1784] -> #1 (btrfs-tree-00){++++}-{3:3}: [6.1794] lock_release+0x127/0x2a0 [6.1801] up_read+0x1b/0x30 [6.1808] btrfs_search_slot+0x8e0/0xff0 [6.1817] btrfs_lookup_inode+0x52/0xd0 [6.1825] __btrfs_update_delayed_inode+0x73/0x520 [6.1833] btrfs_commit_inode_delayed_inode+0x11a/0x120 [6.1842] btrfs_log_inode+0x608/0x1aa0 [6.1849] btrfs_log_inode_parent+0x249/0xf80 [6.1857] btrfs_log_dentry_safe+0x3e/0x60 [6.1865] btrfs_sync_file+0x431/0x690 [6.1872] do_fsync+0x39/0x80 [6.1879] __x64_sys_fsync+0x13/0x20 [6.1887] do_syscall_64+0x97/0x3e0 [6.1894] entry_SYSCALL_64_after_hwframe+0x76/0x7e [6.1903] -> #0 (&delayed_node->mutex){+.+.}-{3:3}: [6.1913] __lock_acquire+0x15e9/0x2820 [6.1920] lock_acquire+0xc9/0x2d0 [6.1927] __mutex_lock+0xcc/0x10a0 [6.1934] __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1944] btrfs_evict_inode+0x20b/0x4b0 [6.1952] evict+0x15a/0x2f0 [6.1958] prune_icache_sb+0x91/0xd0 [6.1966] super_cache_scan+0x150/0x1d0 [6.1974] do_shrink_slab+0x155/0x6f0 [6.1981] shrink_slab+0x48e/0x890 [6.1988] shrink_one+0x11a/0x1f0 [6.1995] shrink_node+0xbfd/0x1320 [6.1002] balance_pgdat+0x67f/0xc60 [6.1321] kswapd+0x1dc/0x3e0 [6.1643] kthread+0xff/0x240 [6.1965] ret_from_fork+0x223/0x280 [6.1287] ret_from_fork_asm+0x1a/0x30 [6.1616] other info that might help us debug this: [6.1561] Chain exists of: &delayed_node->mutex --> btrfs-tree-00 --> fs_reclaim [6.1503] Possible unsafe locking scenario: [6.1110] CPU0 CPU1 [6.1411] ---- ---- [6.1707] lock(fs_reclaim); [6.1998] lock(btrfs-tree-00); [6.1291] lock(fs_reclaim); [6.1581] lock(&delayed_node->mutex); [6.1874] *** DEADLOCK *** [6.1716] 2 locks held by kswapd0/117: [6.1999] #0: ffffffffa4ab8ce0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x195/0xc60 [6.1294] #1: ffff8d998344b0e0 (&type->s_umount_key#40){++++}- {3:3}, at: super_cache_scan+0x37/0x1d0 [6.1596] stack backtrace: [6.1183] CPU: 11 UID: 0 PID: 117 Comm: kswapd0 Tainted: G U 6.18.0+ #4 PREEMPT(lazy) [6.1185] Tainted: [U]=USER [6.1186] Hardware name: ASUS System Product Name/PRIME B560M-A AC, BIOS 2001 02/01/2023 [6.1187] Call Trace: [6.1187] [6.1189] dump_stack_lvl+0x6e/0xa0 [6.1192] print_circular_bug.cold+0x17a/0x1c0 [6.1194] check_noncircular+0x175/0x190 [6.1197] __lock_acquire+0x15e9/0x2820 [6.1200] lock_acquire+0xc9/0x2d0 [6.1201] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1204] __mutex_lock+0xcc/0x10a0 [6.1206] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1208] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1211] ? __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1213] __btrfs_release_delayed_node.part.0+0x39/0x2f0 [6.1215] btrfs_evict_inode+0x20b/0x4b0 [6.1217] ? lock_acquire+0xc9/0x2d0 [6.1220] evict+0x15a/0x2f0 [6.1222] prune_icache_sb+0x91/0xd0 [6.1224] super_cache_scan+0x150/0x1d0 [6.1226] do_shrink_slab+0x155/0x6f0 [6.1228] shrink_slab+0x48e/0x890 [6.1229] ? shrink_slab+0x2d2/0x890 [6.1231] shrink_one+0x11a/0x1f0 [6.1234] shrink_node+0xbfd/0x1320 [6.1236] ? shrink_node+0xa2d/0x1320 [6.1236] ? shrink_node+0xbd3/0x1320 [6.1239] ? balance_pgdat+0x67f/0xc60 [6.1239] balance_pgdat+0x67f/0xc60 [6.1241] ? finish_task_switch.isra.0+0xc4/0x2a0 [6.1246] kswapd+0x1dc/0x3e0 [6.1247] ? __pfx_autoremove_wake_function+0x10/0x10 [6.1249] ? __pfx_kswapd+0x10/0x10 [6.1250] kthread+0xff/0x240 [6.1251] ? __pfx_kthread+0x10/0x10 [6.1253] ret_from_fork+0x223/0x280 [6.1255] ? __pfx_kthread+0x10/0x10 [6.1257] ret_from_fork_asm+0x1a/0x30 [6.1260] This is because: 1) The fsync task is holding an inode's delayed node mutex (for a directory) while calling __btrfs_update_delayed_inode() and that needs to do a search on the subvolume's btree (therefore read lock some extent buffers); 2) The lookup task, at btrfs_lookup(), triggered reclaim with the GFP_KERNEL allocation done by btrfs_init_file_extent_tree() while holding a read lock on a subvolume leaf; 3) The reclaim triggered kswapd which is doing inode eviction for the directory inode the fsync task is using as an argument to btrfs_commit_inode_delayed_inode() - but in that call chain we are trying to read lock the same leaf that the lookup task is holding while calling btrfs_init_file_extent_tree() and doing the GFP_KERNEL allocation. Fix this by calling btrfs_init_file_extent_tree() after we don't need the path anymore and release it in btrfs_read_locked_inode(). Reported-by: Thomas Hellström Link: https://lore.kernel.org/linux-btrfs/6e55113a22347c3925458a5d840a18401a38b276.camel@linux.intel.com/ Fixes: 8679d2687c35 ("btrfs: initialize inode::file_extent_tree after i_mode has been set") Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: avoid access-beyond-folio for bs > ps encoded writes

2026-01-06T00:22:59Z

[POTENTIAL BUG] If the system page size is 4K and fs block size is 8K, and max_inline mount option is set to 6K, we can inline a 6K sized data extent. Then a encoded write submitted a compressed extent which is at file offset 0, and the compressed length is 6K, which is allowed to be inlined. Now a read beyond page boundary is triggered inside write_extent_buffer() from insert_inline_extent(). [CAUSE] Currently the function __cow_file_range_inline() can only accept a single folio. For regular compressed write path, we always allocate the compressed folios using the minimal order matching the block size, thus the @compressed_folio should always cover a full fs block thus it is fine. But for encoded writes, they allocate page size folios, this means we can hit a case where the compressed data is smaller than block size but still larger than page size, in that case __cow_file_range_inline() will be called with @compressed_size larger than a page. In that case we will trigger a read beyond the folio inside insert_inline_extent(). Thankfully this is not that common, as the default max_inline is only 2048 bytes, smaller than PAGE_SIZE, and bs > ps support is still experimental. [FIX] We need to either allow insert_inline_extent() to accept a page array to properly support such case, or reject such inline extent. The latter is a much simpler solution, and considering bs > ps will stay as a corner case and non-default max_inline will be even rarer, I don't think we really need to fulfill such niche. So just reject any inline extent that's larger than PAGE_SIZE, and add an extra ASSERT() to insert_inline_extent() to catch such beyond-boundary access. Fixes: ec20799064c8 ("btrfs: enable encoded read/write/send for bs > ps cases") Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

Merge tag 'for-6.19-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

2026-01-05T22:10:48Z

Pull btrfs fixes from David Sterba: - fix potential deadlock due to mismatching transaction states when waiting for the current transaction - fix squota accounting with nested snapshots - fix quota inheritance of qgroups with multiple parent qgroups - fix NULL inode pointer in evict tracepoint - fix writes beyond end of file on systems with 64K page size and 4K block size - fix logging of inodes after exchange rename - fix use after free when using ref_tracker feature - space reservation fixes * tag 'for-6.19-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: btrfs: fix reservation leak in some error paths when inserting inline extent btrfs: do not free data reservation in fallback from inline due to -ENOSPC btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node() btrfs: always detect conflicting inodes when logging inode refs btrfs: fix beyond-EOF write handling btrfs: fix deadlock in wait_current_trans() due to ignored transaction type btrfs: fix NULL dereference on root when tracing inode eviction btrfs: qgroup: update all parent qgroups when doing quick inherit btrfs: fix qgroup_snapshot_quick_inherit() squota bug

btrfs: fix reservation leak in some error paths when inserting inline extent

2025-12-16T21:53:15Z

If we fail to allocate a path or join a transaction, we return from __cow_file_range_inline() without freeing the reserved qgroup data, resulting in a leak. Fix this by ensuring we call btrfs_qgroup_free_data() in such cases. Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: do not free data reservation in fallback from inline due to -ENOSPC

2025-12-16T21:53:15Z

If we fail to create an inline extent due to -ENOSPC, we will attempt to go through the normal COW path, reserve an extent, create an ordered extent, etc. However we were always freeing the reserved qgroup data, which is wrong since we will use data. Fix this by freeing the reserved qgroup data in __cow_file_range_inline() only if we are not doing the fallback (ret is <= 0). Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba