kernel/fs, branch linux-6.12.y

ext4: fix potential null deref in ext4_mb_init()

2026-03-13T16:20:48Z

commit 3c3fac6bc0a9c00dbe65d8dc0d3a282afe4d3188 upstream. In ext4_mb_init(), ext4_mb_avg_fragment_size_destroy() may be called when sbi->s_mb_avg_fragment_size remains uninitialized (e.g., if groupinfo slab cache allocation fails). Since ext4_mb_avg_fragment_size_destroy() lacks null pointer checking, this leads to a null pointer dereference. ================================================================== EXT4-fs: no memory for groupinfo slab cache BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 0 P4D 0 Oops: Oops: 0002 [#1] SMP PTI CPU:2 UID: 0 PID: 87 Comm:mount Not tainted 6.17.0-rc2 #1134 PREEMPT(none) RIP: 0010:_raw_spin_lock_irqsave+0x1b/0x40 Call Trace: xa_destroy+0x61/0x130 ext4_mb_init+0x483/0x540 __ext4_fill_super+0x116d/0x17b0 ext4_fill_super+0xd3/0x280 get_tree_bdev_flags+0x132/0x1d0 vfs_get_tree+0x29/0xd0 do_new_mount+0x197/0x300 __x64_sys_mount+0x116/0x150 do_syscall_64+0x50/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e ================================================================== Therefore, add necessary null check to ext4_mb_avg_fragment_size_destroy() to prevent this issue. The same fix is also applied to ext4_mb_largest_free_orders_destroy(). Reported-by: syzbot+1713b1aa266195b916c2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1713b1aa266195b916c2 Cc: stable@kernel.org Fixes: f7eaacbb4e54 ("ext4: convert free groups order lists to xarrays") Signed-off-by: Baokun Li Reviewed-by: Zhang Yi Reviewed-by: Ritesh Harjani (IBM) Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

smb/client: fix buffer size for smb311_posix_qinfo in SMB311_posix_query_info()

2026-03-13T16:20:43Z

[ Upstream commit 9621b996e4db1dbc2b3dc5d5910b7d6179397320 ] SMB311_posix_query_info() is currently unused, but it may still be used in some stable versions, so these changes are submitted as a separate patch. Use `sizeof(struct smb311_posix_qinfo)` instead of sizeof its pointer, so the allocated buffer matches the actual struct size. Fixes: b1bc1874b885 ("smb311: Add support for SMB311 query info (non-compounded)") Reported-by: ChenXiaoSong Signed-off-by: ZhangGuoDong Reviewed-by: ChenXiaoSong Signed-off-by: Steve French Signed-off-by: Sasha Levin

smb/client: fix buffer size for smb311_posix_qinfo in smb2_compound_op()

2026-03-13T16:20:43Z

[ Upstream commit 12c43a062acb0ac137fc2a4a106d4d084b8c5416 ] Use `sizeof(struct smb311_posix_qinfo)` instead of sizeof its pointer, so the allocated buffer matches the actual struct size. Fixes: 6a5f6592a0b6 ("SMB311: Add support for query info using posix extensions (level 100)") Reported-by: ChenXiaoSong Signed-off-by: ZhangGuoDong Reviewed-by: ChenXiaoSong Signed-off-by: Steve French Signed-off-by: Sasha Levin

btrfs: always fallback to buffered write if the inode requires checksum

2026-03-13T16:20:36Z

commit 968f19c5b1b7d5595423b0ac0020cc18dfed8cb5 upstream. [BUG] It is a long known bug that VM image on btrfs can lead to data csum mismatch, if the qemu is using direct-io for the image (this is commonly known as cache mode 'none'). [CAUSE] Inside the VM, if the fs is EXT4 or XFS, or even NTFS from Windows, the fs is allowed to dirty/modify the folio even if the folio is under writeback (as long as the address space doesn't have AS_STABLE_WRITES flag inherited from the block device). This is a valid optimization to improve the concurrency, and since these filesystems have no extra checksum on data, the content change is not a problem at all. But the final write into the image file is handled by btrfs, which needs the content not to be modified during writeback, or the checksum will not match the data (checksum is calculated before submitting the bio). So EXT4/XFS/NTRFS assume they can modify the folio under writeback, but btrfs requires no modification, this leads to the false csum mismatch. This is only a controlled example, there are even cases where multi-thread programs can submit a direct IO write, then another thread modifies the direct IO buffer for whatever reason. For such cases, btrfs has no sane way to detect such cases and leads to false data csum mismatch. [FIX] I have considered the following ideas to solve the problem: - Make direct IO to always skip data checksum This not only requires a new incompatible flag, as it breaks the current per-inode NODATASUM flag. But also requires extra handling for no csum found cases. And this also reduces our checksum protection. - Let hardware handle all the checksum AKA, just nodatasum mount option. That requires trust for hardware (which is not that trustful in a lot of cases), and it's not generic at all. - Always fallback to buffered write if the inode requires checksum This was suggested by Christoph, and is the solution utilized by this patch. The cost is obvious, the extra buffer copying into page cache, thus it reduces the performance. But at least it's still user configurable, if the end user still wants the zero-copy performance, just set NODATASUM flag for the inode (which is a common practice for VM images on btrfs). Since we cannot trust user space programs to keep the buffer consistent during direct IO, we have no choice but always falling back to buffered IO. At least by this, we avoid the more deadly false data checksum mismatch error. Suggested-by: Christoph Hellwig Reviewed-by: Filipe Manana Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman

xattr: switch to CLASS(fd)

2026-03-13T16:20:36Z

commit a71874379ec8c6e788a61d71b3ad014a8d9a5c08 upstream. Reviewed-by: Christian Brauner Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman

smb: client: Don't log plaintext credentials in cifs_set_cifscreds

2026-03-13T16:20:36Z

commit 2f37dc436d4e61ff7ae0b0353cf91b8c10396e4d upstream. When debug logging is enabled, cifs_set_cifscreds() logs the key payload and exposes the plaintext username and password. Remove the debug log to avoid exposing credentials. Fixes: 8a8798a5ff90 ("cifs: fetch credentials out of keyring for non-krb5 auth multiuser mounts") Cc: stable@vger.kernel.org Acked-by: Paulo Alcantara (Red Hat) Signed-off-by: Thorsten Blum Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: fix broken multichannel with krb5+signing

2026-03-13T16:20:35Z

commit d9d1e319b39ea685ede59319002d567c159d23c3 upstream. When mounting a share with 'multichannel,max_channels=n,sec=krb5i', the client was duplicating signing key for all secondary channels, thus making the server fail all commands sent from secondary channels due to bad signatures. Every channel has its own signing key, so when establishing a new channel with krb5 auth, make sure to use the new session key as the derived key to generate channel's signing key in SMB2_auth_kerberos(). Repro: $ mount.cifs //srv/share /mnt -o multichannel,max_channels=4,sec=krb5i $ sleep 5 $ umount /mnt $ dmesg ... CIFS: VFS: sign fail cmd 0x5 message id 0x2 CIFS: VFS: \\srv SMB signature verification returned error = -13 CIFS: VFS: sign fail cmd 0x5 message id 0x2 CIFS: VFS: \\srv SMB signature verification returned error = -13 CIFS: VFS: sign fail cmd 0x4 message id 0x2 CIFS: VFS: \\srv SMB signature verification returned error = -13 Reported-by: Xiaoli Feng Reviewed-by: Enzo Matsumiya Signed-off-by: Paulo Alcantara (Red Hat) Cc: David Howells Cc: linux-cifs@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

smb: client: fix cifs_pick_channel when channels are equally loaded

2026-03-13T16:20:35Z

commit 663c28469d3274d6456f206a6671c91493d85ff1 upstream. cifs_pick_channel uses (start % chan_count) when channels are equally loaded, but that can return a channel that failed the eligibility checks. Drop the fallback and return the scan-selected channel instead. If none is eligible, keep the existing behavior of using the primary channel. Signed-off-by: Henrique Carvalho Acked-by: Paulo Alcantara (Red Hat) Acked-by: Meetakshi Setiya Reviewed-by: Shyam Prasad N Cc: stable@vger.kernel.org Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

Squashfs: check metadata block offset is within range

2026-03-13T16:20:35Z

commit fdb24a820a5832ec4532273282cbd4f22c291a0d upstream. Syzkaller reports a "general protection fault in squashfs_copy_data" This is ultimately caused by a corrupted index look-up table, which produces a negative metadata block offset. This is subsequently passed to squashfs_copy_data (via squashfs_read_metadata) where the negative offset causes an out of bounds access. The fix is to check that the offset is within range in squashfs_read_metadata. This will trap this and other cases. Link: https://lkml.kernel.org/r/20260217050955.138351-1-phillip@squashfs.org.uk Fixes: f400e12656ab ("Squashfs: cache operations") Reported-by: syzbot+a9747fe1c35a5b115d3f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/699234e2.a70a0220.2c38d7.00e2.GAE@google.com/ Signed-off-by: Phillip Lougher Cc: Christian Brauner Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

nfsd: Fix cred ref leak in nfsd_nl_threads_set_doit().

2026-03-13T16:20:35Z

commit 1cb968a2013ffa8112d52ebe605009ea1c6a582c upstream. syzbot reported memory leak of struct cred. [0] nfsd_nl_threads_set_doit() passes get_current_cred() to nfsd_svc(), but put_cred() is not called after that. The cred is finally passed down to _svc_xprt_create(), which calls get_cred() with the cred for struct svc_xprt. The ownership of the refcount by get_current_cred() is not transferred to anywhere and is just leaked. nfsd_svc() is also called from write_threads(), but it does not bump file->f_cred there. nfsd_nl_threads_set_doit() is called from sendmsg() and current->cred does not go away. Let's use current_cred() in nfsd_nl_threads_set_doit(). [0]: BUG: memory leak unreferenced object 0xffff888108b89480 (size 184): comm "syz-executor", pid 5994, jiffies 4294943386 hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 369454a7): kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline] slab_post_alloc_hook mm/slub.c:4958 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x412/0x580 mm/slub.c:5270 prepare_creds+0x22/0x600 kernel/cred.c:185 copy_creds+0x44/0x290 kernel/cred.c:286 copy_process+0x7a7/0x2870 kernel/fork.c:2086 kernel_clone+0xac/0x6e0 kernel/fork.c:2651 __do_sys_clone+0x7f/0xb0 kernel/fork.c:2792 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 924f4fb003ba ("NFSD: convert write_threads to netlink command") Cc: stable@vger.kernel.org Reported-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/69744674.a00a0220.33ccc7.0000.GAE@google.com/ Tested-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com Signed-off-by: Kuniyuki Iwashima Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman