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author | Vlastimil Babka <vbabka@suse.cz> | 2020-08-07 09:19:01 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-07 21:33:22 +0300 |
commit | d3c58f24be1bf10fa9e11977080a2398ddcd8361 (patch) | |
tree | cc1fe9180c171864baa4b3674f055257d5641cb5 /mm/slub.c | |
parent | 8fc8d6664247a6e65cba000789e2e85e2288f6f7 (diff) | |
download | linux-d3c58f24be1bf10fa9e11977080a2398ddcd8361.tar.xz |
mm, slab/slub: move and improve cache_from_obj()
The function cache_from_obj() was added by commit b9ce5ef49f00 ("sl[au]b:
always get the cache from its page in kmem_cache_free()") to support
kmemcg, where per-memcg cache can be different from the root one, so we
can't use the kmem_cache pointer given to kmem_cache_free().
Prior to that commit, SLUB already had debugging check+warning that could
be enabled to compare the given kmem_cache pointer to one referenced by
the slab page where the object-to-be-freed resides. This check was moved
to cache_from_obj(). Later the check was also enabled for
SLAB_FREELIST_HARDENED configs by commit 598a0717a816 ("mm/slab: validate
cache membership under freelist hardening").
These checks and warnings can be useful especially for the debugging,
which can be improved. Commit 598a0717a816 changed the pr_err() with
WARN_ON_ONCE() to WARN_ONCE() so only the first hit is now reported,
others are silent. This patch changes it to WARN() so that all errors are
reported.
It's also useful to print SLUB allocation/free tracking info for the
offending object, if tracking is enabled. We could export the SLUB
print_tracking() function and provide an empty one for SLAB, or realize
that both the debugging and hardening cases in cache_from_obj() are only
supported by SLUB anyway. So this patch moves cache_from_obj() from
slab.h to separate instances in slab.c and slub.c, where the SLAB version
only does the kmemcg lookup and even could be completely removed once the
kmemcg rework [1] is merged. The SLUB version can thus easily use the
print_tracking() function. It can also use the kmem_cache_debug_flags()
static key check for improved performance in kernels without the hardening
and with debugging not enabled on boot.
[1] https://lore.kernel.org/r/20200608230654.828134-18-guro@fb.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Link: http://lkml.kernel.org/r/20200610163135.17364-10-vbabka@suse.cz
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r-- | mm/slub.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/mm/slub.c b/mm/slub.c index 0b80a8409836..6a99a3c945cb 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1525,6 +1525,10 @@ static bool freelist_corrupted(struct kmem_cache *s, struct page *page, { return false; } + +static void print_tracking(struct kmem_cache *s, void *object) +{ +} #endif /* CONFIG_SLUB_DEBUG */ /* @@ -3171,6 +3175,23 @@ void ___cache_free(struct kmem_cache *cache, void *x, unsigned long addr) } #endif +static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) +{ + struct kmem_cache *cachep; + + if (!IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) && + !memcg_kmem_enabled() && + !kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) + return s; + + cachep = virt_to_cache(x); + if (WARN(cachep && !slab_equal_or_root(cachep, s), + "%s: Wrong slab cache. %s but object is from %s\n", + __func__, s->name, cachep->name)) + print_tracking(cachep, x); + return cachep; +} + void kmem_cache_free(struct kmem_cache *s, void *x) { s = cache_from_obj(s, x); |