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authorStephen Boyd <swboyd@chromium.org>2021-06-29 05:34:52 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-29 20:53:47 +0300
commit792702911f581f7793962fbeb99d5c3a1b28f4c3 (patch)
treed5a5a1ba95e9e6c14e3390db40533f99346be378 /mm/slub.c
parent582d1212edc73e6459d5219a24f312799877b61e (diff)
downloadlinux-792702911f581f7793962fbeb99d5c3a1b28f4c3.tar.xz
slub: force on no_hash_pointers when slub_debug is enabled
Obscuring the pointers that slub shows when debugging makes for some confusing slub debug messages: Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17 Those addresses are hashed for kernel security reasons. If we're trying to be secure with slub_debug on the commandline we have some big problems given that we dump whole chunks of kernel memory to the kernel logs. Let's force on the no_hash_pointers commandline flag when slub_debug is on the commandline. This makes slub debug messages more meaningful and if by chance a kernel address is in some slub debug object dump we will have a better chance of figuring out what went wrong. Note that we don't use %px in the slub code because we want to reduce the number of places that %px is used in the kernel. This also nicely prints a big fat warning at kernel boot if slub_debug is on the commandline so that we know that this kernel shouldn't be used on production systems. [akpm@linux-foundation.org: fix build with CONFIG_SLUB_DEBUG=n] Link: https://lkml.kernel.org/r/20210601182202.3011020-5-swboyd@chromium.org Signed-off-by: Stephen Boyd <swboyd@chromium.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Petr Mladek <pmladek@suse.com> Cc: Joe Perches <joe@perches.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: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
-rw-r--r--mm/slub.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/mm/slub.c b/mm/slub.c
index f8e4d37c4641..4b2ba9c099c9 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -118,12 +118,26 @@
*/
#ifdef CONFIG_SLUB_DEBUG
+
#ifdef CONFIG_SLUB_DEBUG_ON
DEFINE_STATIC_KEY_TRUE(slub_debug_enabled);
#else
DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
#endif
-#endif
+
+static inline bool __slub_debug_enabled(void)
+{
+ return static_branch_unlikely(&slub_debug_enabled);
+}
+
+#else /* CONFIG_SLUB_DEBUG */
+
+static inline bool __slub_debug_enabled(void)
+{
+ return false;
+}
+
+#endif /* CONFIG_SLUB_DEBUG */
static inline bool kmem_cache_debug(struct kmem_cache *s)
{
@@ -4487,6 +4501,10 @@ void __init kmem_cache_init(void)
if (debug_guardpage_minorder())
slub_max_order = 0;
+ /* Print slub debugging pointers without hashing */
+ if (__slub_debug_enabled())
+ no_hash_pointers_enable(NULL);
+
kmem_cache_node = &boot_kmem_cache_node;
kmem_cache = &boot_kmem_cache;