From c0837e021d90fca1b72fa19ff0e7a68136bcde2c Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 15 Jun 2021 18:23:19 -0700 Subject: [PATCH] mm/slub: clarify verification reporting commit 8669dbab2ae56085c128894b181c2aa50f97e368 upstream. Patch series "Actually fix freelist pointer vs redzoning", v4. This fixes redzoning vs the freelist pointer (both for middle-position and very small caches). Both are "theoretical" fixes, in that I see no evidence of such small-sized caches actually be used in the kernel, but that's no reason to let the bugs continue to exist, especially since people doing local development keep tripping over it. :) This patch (of 3): Instead of repeating "Redzone" and "Poison", clarify which sides of those zones got tripped. Additionally fix column alignment in the trailer. Before: BUG test (Tainted: G B ): Redzone overwritten ... Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Object (____ptrval____): f6 f4 a5 40 1d e8 ...@.. Redzone (____ptrval____): 1a aa .. Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ After: BUG test (Tainted: G B ): Right Redzone overwritten ... Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Object (____ptrval____): f6 f4 a5 40 1d e8 ...@.. Redzone (____ptrval____): 1a aa .. Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........ The earlier commits that slowly resulted in the "Before" reporting were: d86bd1bece6f ("mm/slub: support left redzone") ffc79d288000 ("slub: use print_hex_dump") 2492268472e7 ("SLUB: change error reporting format to follow lockdep loosely") Link: https://lkml.kernel.org/r/20210608183955.280836-1-keescook@chromium.org Link: https://lkml.kernel.org/r/20210608183955.280836-2-keescook@chromium.org Link: https://lore.kernel.org/lkml/cfdb11d7-fb8e-e578-c939-f7f5fb69a6bd@suse.cz/ Signed-off-by: Kees Cook Acked-by: Vlastimil Babka Cc: Marco Elver Cc: "Lin, Zhenpeng" Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Roman Gushchin Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- Documentation/vm/slub.rst | 10 +++++----- mm/slub.c | 14 +++++++------- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/Documentation/vm/slub.rst b/Documentation/vm/slub.rst index 933ada4368ff..309c1acb414b 100644 --- a/Documentation/vm/slub.rst +++ b/Documentation/vm/slub.rst @@ -160,7 +160,7 @@ SLUB Debug output Here is a sample of slub debug output:: ==================================================================== - BUG kmalloc-8: Redzone overwritten + BUG kmalloc-8: Right Redzone overwritten -------------------------------------------------------------------- INFO: 0xc90f6d28-0xc90f6d2b. First byte 0x00 instead of 0xcc @@ -168,10 +168,10 @@ Here is a sample of slub debug output:: INFO: Object 0xc90f6d20 @offset=3360 fp=0xc90f6d58 INFO: Allocated in get_modalias+0x61/0xf5 age=53 cpu=1 pid=554 - Bytes b4 0xc90f6d10: 00 00 00 00 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ - Object 0xc90f6d20: 31 30 31 39 2e 30 30 35 1019.005 - Redzone 0xc90f6d28: 00 cc cc cc . - Padding 0xc90f6d50: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ + Bytes b4 (0xc90f6d10): 00 00 00 00 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ + Object (0xc90f6d20): 31 30 31 39 2e 30 30 35 1019.005 + Redzone (0xc90f6d28): 00 cc cc cc . + Padding (0xc90f6d50): 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ [] dump_trace+0x63/0x1eb [] show_trace_log_lvl+0x1a/0x2f diff --git a/mm/slub.c b/mm/slub.c index 52ded855b4ed..5d6d3ba38566 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -688,15 +688,15 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p) p, p - addr, get_freepointer(s, p)); if (s->flags & SLAB_RED_ZONE) - print_section(KERN_ERR, "Redzone ", p - s->red_left_pad, + print_section(KERN_ERR, "Redzone ", p - s->red_left_pad, s->red_left_pad); else if (p > addr + 16) print_section(KERN_ERR, "Bytes b4 ", p - 16, 16); - print_section(KERN_ERR, "Object ", p, + print_section(KERN_ERR, "Object ", p, min_t(unsigned int, s->object_size, PAGE_SIZE)); if (s->flags & SLAB_RED_ZONE) - print_section(KERN_ERR, "Redzone ", p + s->object_size, + print_section(KERN_ERR, "Redzone ", p + s->object_size, s->inuse - s->object_size); off = get_info_end(s); @@ -708,7 +708,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p) if (off != size_from_object(s)) /* Beginning of the filler is the free pointer */ - print_section(KERN_ERR, "Padding ", p + off, + print_section(KERN_ERR, "Padding ", p + off, size_from_object(s) - off); dump_stack(); @@ -882,11 +882,11 @@ static int check_object(struct kmem_cache *s, struct page *page, u8 *endobject = object + s->object_size; if (s->flags & SLAB_RED_ZONE) { - if (!check_bytes_and_report(s, page, object, "Redzone", + if (!check_bytes_and_report(s, page, object, "Left Redzone", object - s->red_left_pad, val, s->red_left_pad)) return 0; - if (!check_bytes_and_report(s, page, object, "Redzone", + if (!check_bytes_and_report(s, page, object, "Right Redzone", endobject, val, s->inuse - s->object_size)) return 0; } else { @@ -901,7 +901,7 @@ static int check_object(struct kmem_cache *s, struct page *page, if (val != SLUB_RED_ACTIVE && (s->flags & __OBJECT_POISON) && (!check_bytes_and_report(s, page, p, "Poison", p, POISON_FREE, s->object_size - 1) || - !check_bytes_and_report(s, page, p, "Poison", + !check_bytes_and_report(s, page, p, "End Poison", p + s->object_size - 1, POISON_END, 1))) return 0; /*