On Tue, Jul 29, 2025 at 04:14:55PM +0800, Li Qiong wrote:
For debugging, object_err() prints free pointer of the object. However, if check_valid_pointer() returns false for a object, dereferncing `object + s->offset` can lead to a crash. Therefore, print the object's address in such cases.
As the code changed a bit, I think the commit message could better reflect what this patch actually does.
Fixes: bb192ed9aa71 ("mm/slub: Convert most struct page to struct slab by spatch")
As Vlastimil mentioned in previous version, this is not the first commit that introduced this problem.
Cc: stable@vger.kernel.org Signed-off-by: Li Qiong liqiong@nfschina.com
v2:
- rephrase the commit message, add comment for object_err().
v3:
- check object pointer in object_err().
mm/slub.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c index 31e11ef256f9..d3abae5a2193 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1104,7 +1104,11 @@ static void object_err(struct kmem_cache *s, struct slab *slab, return; slab_bug(s, reason);
- print_trailer(s, slab, object);
- if (!check_valid_pointer(s, slab, object)) {
print_slab_info(slab);pr_err("invalid object 0x%p\n", object);
Can we just handle this inside print_trailer() because that's the function that prints the object's free pointer, metadata, etc.?
Also, the message should start with a capital letter.
and "invalid object" sounds misleading because it's the pointer that is invalid. Perhaps simply "Invalid pointer 0x%p\n"? (What would be the most comprehensive message here? :P)
- } else
print_trailer(s, slab, object);
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); WARN_ON(1); @@ -1587,7 +1591,7 @@ static inline int alloc_consistency_checks(struct kmem_cache *s, return 0; if (!check_valid_pointer(s, slab, object)) {
object_err(s, slab, object, "Freelist Pointer check fails");
slab_err(s, slab, "Freelist Pointer(0x%p) check fails", object);
Do we really need this hunk after making object_err() resiliant against wild pointers?
}