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mm, slab/slub: improve error reporting and overhead of cache_from_obj() 

cache_from_obj() was added by commit b9ce5ef49f ("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 598a0717a8 ("mm/slab: validate
cache membership under freelist hardening").

These checks and warnings can be useful especially for the debugging,
which can be improved.  Commit 598a0717a8 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.  Thus, export the SLUB
print_tracking() function and provide an empty one for SLAB.

For SLUB we can also benefit from the static key check in
kmem_cache_debug_flags(), but we need to move this function to slab.h and
declare the static key there.

[1] https://lore.kernel.org/r/20200608230654.828134-18-guro@fb.com

[vbabka@suse.cz: avoid bogus WARN()]
  Link: https://lore.kernel.org/r/20200623090213.GW5535@shao2-debian
  Link: http://lkml.kernel.org/r/b33e0fa7-cd28-4788-9e54-5927846329ef@suse.cz

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Garrett <mjg59@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Link: http://lkml.kernel.org/r/afeda7ac-748b-33d8-a905-56b708148ad5@suse.cz
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vlastimil Babka 2020-08-06 23:19:05 -07:00 committed by Linus Torvalds
parent d3c58f24be
commit e42f174e43
3 changed files with 46 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
mm/slab.c
View File

@ -3678,14 +3678,6 @@ void *__kmalloc_track_caller(size_t size, gfp_t flags, unsigned long caller)
}
EXPORT_SYMBOL(__kmalloc_track_caller);
static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
{
if (memcg_kmem_enabled())
return virt_to_cache(x);
else
return s;
}
/**
* kmem_cache_free - Deallocate an object
* @cachep: The cache the allocation was from.

45
mm/slab.h
View File

@ -276,6 +276,34 @@ static inline int cache_vmstat_idx(struct kmem_cache *s)
NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE;
}
#ifdef CONFIG_SLUB_DEBUG
#ifdef CONFIG_SLUB_DEBUG_ON
DECLARE_STATIC_KEY_TRUE(slub_debug_enabled);
#else
DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
#endif
extern void print_tracking(struct kmem_cache *s, void *object);
#else
static inline void print_tracking(struct kmem_cache *s, void *object)
{
}
#endif
/*
* Returns true if any of the specified slub_debug flags is enabled for the
* cache. Use only for flags parsed by setup_slub_debug() as it also enables
* the static key.
*/
static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
{
#ifdef CONFIG_SLUB_DEBUG
VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS));
if (static_branch_unlikely(&slub_debug_enabled))
return s->flags & flags;
#endif
return false;
}
#ifdef CONFIG_MEMCG_KMEM
/* List of all root caches. */
@ -504,6 +532,23 @@ static __always_inline void uncharge_slab_page(struct page *page, int order,
memcg_uncharge_slab(page, order, s);
}
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;
}
static inline size_t slab_ksize(const struct kmem_cache *s)
{
#ifndef CONFIG_SLUB

38
mm/slub.c
View File

@ -122,21 +122,6 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
#endif
#endif
/*
* Returns true if any of the specified slub_debug flags is enabled for the
* cache. Use only for flags parsed by setup_slub_debug() as it also enables
* the static key.
*/
static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
{
VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS));
#ifdef CONFIG_SLUB_DEBUG
if (static_branch_unlikely(&slub_debug_enabled))
return s->flags & flags;
#endif
return false;
}
static inline bool kmem_cache_debug(struct kmem_cache *s)
{
return kmem_cache_debug_flags(s, SLAB_DEBUG_FLAGS);
@ -653,7 +638,7 @@ static void print_track(const char *s, struct track *t, unsigned long pr_time)
#endif
}
static void print_tracking(struct kmem_cache *s, void *object)
void print_tracking(struct kmem_cache *s, void *object)
{
unsigned long pr_time = jiffies;
if (!(s->flags & SLAB_STORE_USER))
@ -1525,10 +1510,6 @@ 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 */
/*
@ -3175,23 +3156,6 @@ 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);