[PATCH] mm/slub: do not place freelist pointer to middle of object if redzone is on
From: Changbin Du
Date: Sat Apr 25 2020 - 05:14:00 EST
The recent kernel fails to boot when slub redzone is turned on. This is
caused by commit 3202fa62fb ("slub: relocate freelist pointer to middle of
object") which relocates freelist pointer to middle of object. In this
case, get_track() gets a wrong address and then the redzone is overwritten.
This patch fixes it by relocating freelist pointer after the object, as
what slub posion does.
[ 2.390256][ T0] =============================================================================
[ 2.392816][ T0] BUG kmem_cache_node (Not tainted): Redzone overwritten
[ 2.393735][ T0] -----------------------------------------------------------------------------
[ 2.393735][ T0]
[ 2.395168][ T0] Disabling lock debugging due to kernel taint
[ 2.395923][ T0] INFO: 0xffff88805c000380-0xffff88805c000387 @offset=896. First byte 0x0 instead of 0xbb
[ 2.397175][ T0] INFO: Slab 0xffffea0001700000 objects=25 used=25 fp=0x0000000000000000 flags=0xfffffc0010200
[ 2.398882][ T0] INFO: Object 0xffff88805c000300 @offset=768 fp=0xffff88805c000580
[ 2.398882][ T0]
[ 2.400145][ T0] Redzone ffff88805c000280: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.401593][ T0] Redzone ffff88805c000290: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.403825][ T0] Redzone ffff88805c0002a0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.405853][ T0] Redzone ffff88805c0002b0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.407714][ T0] Redzone ffff88805c0002c0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.411066][ T0] Redzone ffff88805c0002d0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.413818][ T0] Redzone ffff88805c0002e0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.415482][ T0] Redzone ffff88805c0002f0: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................
[ 2.416975][ T0] Object ffff88805c000300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.418445][ T0] Object ffff88805c000310: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.420183][ T0] Object ffff88805c000320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.421911][ T0] Object ffff88805c000330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.423491][ T0] Object ffff88805c000340: 00 00 00 00 00 00 00 00 e8 ed 4a b9 09 7b 20 83 ..........J..{ .
[ 2.425186][ T0] Object ffff88805c000350: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.426901][ T0] Object ffff88805c000360: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.428673][ T0] Object ffff88805c000370: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.430431][ T0] Redzone ffff88805c000380: 00 00 00 00 00 00 00 00 ........
[ 2.485141][ T0] Padding ffff88805c000490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.494198][ T0] Padding ffff88805c0004a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.503094][ T0] Padding ffff88805c0004b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.578370][ T0] Padding ffff88805c0004c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.584420][ T0] Padding ffff88805c0004d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.590139][ T0] Padding ffff88805c0004e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.596915][ T0] Padding ffff88805c0004f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
[ 2.604002][ T0] CPU: 0 PID: 0 Comm: swapper Tainted: G B 5.7.0-rc1+ #53
[ 2.608493][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
[ 2.612959][ T0] Call Trace:
[ 2.613953][ T0] dump_stack+0x8c/0xc0
[ 2.615063][ T0] check_bytes_and_report.cold+0x60/0x95
[ 2.616572][ T0] check_object+0x1c1/0x280
[ 2.617462][ T0] ? pvclock_clocksource_read+0xf6/0x1c0
[ 2.618646][ T0] ? __kmem_cache_create+0x16a/0x670
[ 2.619692][ T0] alloc_debug_processing+0x129/0x170
[ 2.620766][ T0] ___slab_alloc+0x58c/0x630
[ 2.621804][ T0] ? __kmem_cache_create+0x16a/0x670
[ 2.622631][ T0] ? print_unlock_imbalance_bug+0x40/0x40
[ 2.623630][ T0] ? lock_acquire+0x11f/0x200
[ 2.624421][ T0] ? __kmem_cache_create+0x16a/0x670
[ 2.625342][ T0] ? __slab_alloc+0x1c/0x30
[ 2.626106][ T0] ? ___slab_alloc+0x5/0x630
[ 2.626890][ T0] __slab_alloc+0x1c/0x30
[ 2.627500][ T0] kmem_cache_alloc_node+0xab/0x2e0
[ 2.628222][ T0] __kmem_cache_create+0x16a/0x670
[ 2.628883][ T0] ? mem_init_print_info+0x2af/0x2be
[ 2.629596][ T0] create_boot_cache+0xa4/0xc8
[ 2.630282][ T0] kmem_cache_init+0x80/0x14a
[ 2.631233][ T0] start_kernel+0x67a/0xa2a
[ 2.631905][ T0] ? thread_stack_cache_init+0x6/0x6
[ 2.632553][ T0] ? x86_family+0x5/0x20
[ 2.633085][ T0] ? load_ucode_bsp+0x50/0x216
[ 2.633629][ T0] secondary_startup_64+0xa4/0xb0
[ 2.634243][ T0] FIX kmem_cache_node: Restoring 0xffff88805c000380-0xffff88805c000387=0xbb
[ 2.634243][ T0]
[ 2.635532][ T0] FIX kmem_cache_node: Marking all objects used
[ 2.636287][ T0] =============================================================================
Fixes: 3202fa62fb ("slub: relocate freelist pointer to middle of object")
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
---
mm/slub.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/slub.c b/mm/slub.c
index 332d4b459a90..59c5b49038b0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3570,7 +3570,7 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
*/
s->inuse = size;
- if (((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)) ||
+ if (((flags & (SLAB_TYPESAFE_BY_RCU | SLAB_RED_ZONE | SLAB_POISON)) ||
s->ctor)) {
/*
* Relocate free pointer after the object if it is not
--
2.25.1