diff options
| author | Harry Yoo <harry.yoo@oracle.com> | 2026-02-10 17:18:59 +0900 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2026-03-04 07:21:37 -0500 |
| commit | efd767ddcef0669bbd33c6a823ea0a88f06d4b29 (patch) | |
| tree | 6dad98a8715f48dde7e6453c7202404e288040ea /mm | |
| parent | da8f341cf65ca40230433dea2206b79ef16a5b5d (diff) | |
mm/slab: do not access current->mems_allowed_seq if !allow_spin
[ Upstream commit 144080a5823b2dbd635acb6decf7ab23182664f3 ]
Lockdep complains when get_from_any_partial() is called in an NMI
context, because current->mems_allowed_seq is seqcount_spinlock_t and
not NMI-safe:
================================
WARNING: inconsistent lock state
6.19.0-rc5-kfree-rcu+ #315 Tainted: G N
--------------------------------
inconsistent {INITIAL USE} -> {IN-NMI} usage.
kunit_try_catch/9989 [HC1[1]:SC0[0]:HE0:SE1] takes:
ffff889085799820 (&____s->seqcount#3){.-.-}-{0:0}, at: ___slab_alloc+0x58f/0xc00
{INITIAL USE} state was registered at:
lock_acquire+0x185/0x320
kernel_init_freeable+0x391/0x1150
kernel_init+0x1f/0x220
ret_from_fork+0x736/0x8f0
ret_from_fork_asm+0x1a/0x30
irq event stamp: 56
hardirqs last enabled at (55): [<ffffffff850a68d7>] _raw_spin_unlock_irq+0x27/0x70
hardirqs last disabled at (56): [<ffffffff850858ca>] __schedule+0x2a8a/0x6630
softirqs last enabled at (0): [<ffffffff81536711>] copy_process+0x1dc1/0x6a10
softirqs last disabled at (0): [<0000000000000000>] 0x0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&____s->seqcount#3);
<Interrupt>
lock(&____s->seqcount#3);
*** DEADLOCK ***
According to Documentation/locking/seqlock.rst, seqcount_t is not
NMI-safe and seqcount_latch_t should be used when read path can interrupt
the write-side critical section. In this case, do not access
current->mems_allowed_seq and avoid retry.
Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().")
Cc: stable@vger.kernel.org
Signed-off-by: Harry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20260210081900.329447-2-harry.yoo@oracle.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/slub.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/mm/slub.c b/mm/slub.c index 78946116ecd2..6304a2b7b831 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3610,6 +3610,7 @@ static struct slab *get_any_partial(struct kmem_cache *s, enum zone_type highest_zoneidx = gfp_zone(pc->flags); struct slab *slab; unsigned int cpuset_mems_cookie; + bool allow_spin = gfpflags_allow_spinning(pc->flags); /* * The defrag ratio allows a configuration of the tradeoffs between @@ -3634,7 +3635,15 @@ static struct slab *get_any_partial(struct kmem_cache *s, return NULL; do { - cpuset_mems_cookie = read_mems_allowed_begin(); + /* + * read_mems_allowed_begin() accesses current->mems_allowed_seq, + * a seqcount_spinlock_t that is not NMI-safe. Do not access + * current->mems_allowed_seq and avoid retry when GFP flags + * indicate spinning is not allowed. + */ + if (allow_spin) + cpuset_mems_cookie = read_mems_allowed_begin(); + zonelist = node_zonelist(mempolicy_slab_node(), pc->flags); for_each_zone_zonelist(zone, z, zonelist, highest_zoneidx) { struct kmem_cache_node *n; @@ -3656,7 +3665,7 @@ static struct slab *get_any_partial(struct kmem_cache *s, } } } - } while (read_mems_allowed_retry(cpuset_mems_cookie)); + } while (allow_spin && read_mems_allowed_retry(cpuset_mems_cookie)); #endif /* CONFIG_NUMA */ return NULL; } |