Re: BUG: unable to handle kernel NULL pointer dereference in kmem_cache_free (2)

[Dmitry Vyukov]

On Mon, Dec 31, 2018 at 8:23 AM syzbot
<syzbot+463e2f5d13fc785dd322@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    345671ea0f92 Merge branch 'akpm' (patches from Andrew)
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10442713400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5c0a49d2b5210087
> dashboard link: https://syzkaller.appspot.com/bug?extid=463e2f5d13fc785dd322
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+463e2f5d13fc785dd322@xxxxxxxxxxxxxxxxxxxxxxxxx

Since this involves OOMs and looks like a one-off induced memory corruption:

#syz dup: kernel panic: corrupted stack end in wb_workfn



> FAT-fs (loop1): Directory bread(block 72) failed
> EXT4-fs (loop3): Can't read superblock on 2nd try
> FAT-fs (loop1): Directory bread(block 73) failed
> audit: type=1400 audit(1540684862.923:177): avc:  denied  { mmap_zero }
> for  pid=17455 comm="udevd" scontext=system_u:system_r:kernel_t:s0
> tcontext=system_u:system_r:kernel_t:s0 tclass=memprotect permissive=1
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 17455 Comm: udevd Not tainted 4.19.0+ #85
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:slab_equal_or_root mm/slab.h:228 [inline]
> RIP: 0010:cache_from_obj mm/slab.h:374 [inline]
> RIP: 0010:kmem_cache_free+0x120/0x290 mm/slab.c:3752
> Code: ea ff ff 48 c1 e8 0c 48 c1 e0 06 48 01 d0 48 8b 50 08 48 8d 4a ff 83
> e2 01 48 0f 45 c1 48 8b 40 18 48 39 c3 0f 84 00 ff ff ff <48> 3b 98 80 00
> 00 00 0f 84 11 01 00 00 48 8b 48 58 48 c7 c6 20 0c
> RSP: 0018:ffff88018eb271d8 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffff8801da979480 RCX: ffffea0007658e87
> RDX: 0000000000000000 RSI: ffffffff8139ec96 RDI: 0000000000000007
> RBP: ffff88018eb271f8 R08: ffff88018e3f03c0 R09: ffffed003914bb50
> R10: ffffed003914bb50 R11: ffff8801c8a5da83 R12: ffff8801d963ab10
> R13: ffff8801b37755a0 R14: ffff8801b37755a0 R15: ffff8801b3775590
> FS:  0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000080 CR3: 00000001c0bd1000 CR4: 00000000001426e0
> Call Trace:
>   anon_vma_chain_free mm/rmap.c:134 [inline]
>   unlink_anon_vmas+0x5f0/0xa60 mm/rmap.c:419
>   free_pgtables+0x271/0x380 mm/memory.c:393
>   exit_mmap+0x2cd/0x590 mm/mmap.c:3146
>   __mmput kernel/fork.c:1044 [inline]
>   mmput+0x247/0x610 kernel/fork.c:1065
>   exec_mmap fs/exec.c:1043 [inline]
>   flush_old_exec+0xb91/0x21b0 fs/exec.c:1276
>   load_elf_binary+0xa39/0x5620 fs/binfmt_elf.c:869
>   search_binary_handler+0x17d/0x570 fs/exec.c:1653
>   exec_binprm fs/exec.c:1695 [inline]
>   __do_execve_file.isra.33+0x1661/0x25d0 fs/exec.c:1819
>   do_execveat_common fs/exec.c:1866 [inline]
>   do_execve fs/exec.c:1883 [inline]
>   __do_sys_execve fs/exec.c:1964 [inline]
>   __se_sys_execve fs/exec.c:1959 [inline]
>   __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7ffa0b953207
> Code: Bad RIP value.
> RSP: 002b:00007ffefdbbcde8 EFLAGS: 00000206 ORIG_RAX: 000000000000003b
> RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007ffa0b953207
> RDX: 0000000000e42b70 RSI: 00007ffefdbbcee0 RDI: 00007ffefdbbdef0
> RBP: 0000000000625500 R08: 000000000000405a R09: 000000000000405a
> R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000e42b70
> R13: 0000000000000007 R14: 0000000000d40030 R15: 0000000000000005
> Modules linked in:
> CR2: 0000000000000080
> kobject: 'loop5' (00000000598b220f): kobject_uevent_env
> ---[ end trace fc838222524811c3 ]---
> RIP: 0010:slab_equal_or_root mm/slab.h:228 [inline]
> RIP: 0010:cache_from_obj mm/slab.h:374 [inline]
> RIP: 0010:kmem_cache_free+0x120/0x290 mm/slab.c:3752
> kobject: 'loop5' (00000000598b220f): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
> Code: ea ff ff 48 c1 e8 0c 48 c1 e0 06 48 01 d0 48 8b 50 08 48 8d 4a ff 83
> e2 01 48 0f 45 c1 48 8b 40 18 48 39 c3 0f 84 00 ff ff ff <48> 3b 98 80 00
> 00 00 0f 84 11 01 00 00 48 8b 48 58 48 c7 c6 20 0c
> RSP: 0018:ffff88018eb271d8 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffff8801da979480 RCX: ffffea0007658e87
> kobject: 'loop1' (00000000606593e3): kobject_uevent_env
> kobject: 'loop2' (00000000a62421b8): kobject_uevent_env
> kobject: 'loop1' (00000000606593e3): fill_kobj_path: path
> = '/devices/virtual/block/loop1'
> kobject: 'loop2' (00000000a62421b8): fill_kobj_path: path
> = '/devices/virtual/block/loop2'
> RDX: 0000000000000000 RSI: ffffffff8139ec96 RDI: 0000000000000007
> RBP: ffff88018eb271f8 R08: ffff88018e3f03c0 R09: ffffed003914bb50
> R10: ffffed003914bb50 R11: ffff8801c8a5da83 R12: ffff8801d963ab10
> R13: ffff8801b37755a0 R14: ffff8801b37755a0 R15: ffff8801b3775590
> kasan: CONFIG_KASAN_INLINE enabled
> kobject: 'loop5' (00000000598b220f): kobject_uevent_env
> FS:  00007ffa0c26f7a0(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> kobject: 'loop5' (00000000598b220f): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
> kobject: 'loop2' (00000000a62421b8): kobject_uevent_env
> general protection fault: 0000 [#2] PREEMPT SMP KASAN
> CPU: 1 PID: 16046 Comm: udevd Tainted: G      D           4.19.0+ #85
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:__anon_vma_interval_tree_insert mm/interval_tree.c:72 [inline]
> RIP: 0010:anon_vma_interval_tree_insert+0x179/0x370 mm/interval_tree.c:83
> Code: 03 42 80 3c 3a 00 0f 85 7d 01 00 00 4d 8b 65 00 4d 85 e4 0f 84 a5 00
> 00 00 e8 b3 fc cf ff 49 8d 7c 24 18 48 89 f8 48 c1 e8 03 <42> 80 3c 38 00
> 0f 85 75 01 00 00 4d 8b 6c 24 18 4c 89 f7 4c 89 ee
> RSP: 0018:ffff8801c3396c90 EFLAGS: 00010206
> RAX: 000000000836b159 RBX: ffff8801d8a8eee0 RCX: ffffffff81af3d90
> RDX: 0000000000000000 RSI: ffffffff81af3d0d RDI: 0000000041b58acb
> RBP: ffff8801c3396cd8 R08: ffff880183b76340 R09: 0000000000000000
> R10: 00000000224b4293 R11: ffff880183b76340 R12: 0000000041b58ab3
> R13: ffff8801d963dfc0 R14: 000000000000001f R15: dffffc0000000000
> FS:  00007ffa0c26f7a0(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000930004 CR3: 000000018800a000 CR4: 00000000001426e0
> Call Trace:
>   anon_vma_chain_link mm/rmap.c:144 [inline]
>   anon_vma_clone+0x2f5/0x710 mm/rmap.c:279
>   anon_vma_fork+0xf4/0x820 mm/rmap.c:332
>   dup_mmap kernel/fork.c:539 [inline]
>   dup_mm kernel/fork.c:1317 [inline]
>   copy_mm kernel/fork.c:1372 [inline]
>   copy_process+0x47cc/0x8770 kernel/fork.c:1916
>   _do_fork+0x1cb/0x11d0 kernel/fork.c:2213
>   __do_sys_clone kernel/fork.c:2320 [inline]
>   __se_sys_clone kernel/fork.c:2314 [inline]
>   __x64_sys_clone+0xbf/0x150 kernel/fork.c:2314
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7ffa0b952f46
> Code: f7 d8 64 89 04 25 d4 02 00 00 64 4c 8b 14 25 10 00 00 00 31 d2 49 81
> c2 d0 02 00 00 31 f6 bf 11 00 20 01 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff
> ff 0f 87 31 01 00 00 85 c0 41 89 c4 0f 85 3b 01 00
> RSP: 002b:00007ffefdbbcd80 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
> RAX: ffffffffffffffda RBX: 00007ffefdbbcd80 RCX: 00007ffa0b952f46
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
> RBP: 00007ffefdbbcde0 R08: 0000000000003eae R09: 0000000000003eae
> R10: 00007ffa0c26fa70 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffefdbbcda0 R14: 0000000000000005 R15: 0000000000000005
> Modules linked in:
> kobject: 'loop1' (00000000606593e3): kobject_uevent_env
> kobject: 'loop2' (00000000a62421b8): fill_kobj_path: path
> = '/devices/virtual/block/loop2'
> kobject: 'loop1' (00000000606593e3): fill_kobj_path: path
> = '/devices/virtual/block/loop1'
> EXT4-fs (loop5): Can't read superblock on 2nd try
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> kobject: 'loop4' (000000001ebc1bae): kobject_uevent_env
> kobject: 'loop4' (000000001ebc1bae): fill_kobj_path: path
> = '/devices/virtual/block/loop4'
> CR2: 00000000004ede98 CR3: 00000001c0bd1000 CR4: 00000000001426e0
> FAT-fs (loop1): Directory bread(block 64) failed
> kobject: 'loop5' (00000000598b220f): kobject_uevent_env
> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
> EXT4-fs (loop2): Invalid log block size: 2949122
> kobject: 'loop5' (00000000598b220f): kobject_uevent_env
> FAT-fs (loop1): Directory bread(block 65) failed
> kobject: 'loop5' (00000000598b220f): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
> kobject: 'loop5' (00000000598b220f): fill_kobj_path: path
> = '/devices/virtual/block/loop5'
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
> FAT-fs (loop1): Directory bread(block 66) failed
> kobject: 'loop2' (00000000a62421b8): kobject_uevent_env
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
>
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