I just got this new warning from kmemcheck:
WARNING: kmemcheck: Caught 32-bit read from freed memory (c7806a60)
a06a80c7ecde70c1a04080c700000000a06709c1000000000000000000000000
f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f
^
Pid: 0, comm: swapper Not tainted (2.6.29-rc4 #230)
EIP: 0060:[<c1096df7>] EFLAGS: 00000286 CPU: 0
EIP is at __purge_vmap_area_lazy+0x117/0x140
EAX: 00070f43 EBX: c7806a40 ECX: c1677080 EDX: 00027b66
ESI: 00002001 EDI: c170df0c EBP: c170df00 ESP: c178830c
DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
CR0: 80050033 CR2: c7806b14 CR3: 01775000 CR4: 00000690
DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
DR6: 00004000 DR7: 00000000
[<c1096f3e>] free_unmap_vmap_area_noflush+0x6e/0x70
[<c1096f6a>] remove_vm_area+0x2a/0x70
[<c1097025>] __vunmap+0x45/0xe0
[<c10970de>] vunmap+0x1e/0x30
[<c1008ba5>] text_poke+0x95/0x150
[<c1008ca9>] alternatives_smp_unlock+0x49/0x60
[<c171ef47>] alternative_instructions+0x11b/0x124
[<c171f991>] check_bugs+0xbd/0xdc
[<c17148c5>] start_kernel+0x2ed/0x360
[<c171409e>] __init_begin+0x9e/0xa9
[<ffffffff>] 0xffffffff
It happened here:
$ addr2line -e vmlinux -i c1096df7
mm/vmalloc.c:540
Code:
list_for_each_entry(va, &valist, purge_list)
__free_vmap_area(va);
It's this instruction:
mov 0x20(%ebx),%edx
Which corresponds to a dereference of va->purge_list.next:
(gdb) p ((struct vmap_area *) 0)->purge_list.next
Cannot access memory at address 0x20
It seems that we should use "safe" list traversal here, as the element
is freed inside the loop. Please verify that this is the right fix.
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: <stable@kernel.org> [2.6.28.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cbb766766f