From f66012909e7bf383fcdc5850709ed5716073fdc4 Mon Sep 17 00:00:00 2001 From: Li Qiong Date: Sat, 6 Sep 2025 22:27:33 -0400 Subject: [PATCH] mm/slub: avoid accessing metadata when pointer is invalid in object_err() [ Upstream commit b4efccec8d06ceb10a7d34d7b1c449c569d53770 ] object_err() reports details of an object for further debugging, such as the freelist pointer, redzone, etc. However, if the pointer is invalid, attempting to access object metadata can lead to a crash since it does not point to a valid object. One known path to the crash is when alloc_consistency_checks() determines the pointer to the allocated object is invalid because of a freelist corruption, and calls object_err() to report it. The debug code should report and handle the corruption gracefully and not crash in the process. In case the pointer is NULL or check_valid_pointer() returns false for the pointer, only print the pointer value and skip accessing metadata. Fixes: 81819f0fc828 ("SLUB core") Cc: Signed-off-by: Li Qiong Reviewed-by: Harry Yoo Reviewed-by: Matthew Wilcox (Oracle) Signed-off-by: Vlastimil Babka [ struct page + print_page_info() ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/slub.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/slub.c b/mm/slub.c index b0f637519ac9..30daba09da35 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -729,7 +729,12 @@ void object_err(struct kmem_cache *s, struct page *page, u8 *object, char *reason) { slab_bug(s, "%s", reason); - print_trailer(s, page, object); + if (!object || !check_valid_pointer(s, page, object)) { + print_page_info(page); + pr_err("Invalid pointer 0x%p\n", object); + } else { + print_trailer(s, page, object); + } } static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,