[syzbot] general protection fault in dma_fence_array_first

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8515d05bf6bc Add linux-next specific files for 20220328
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1694e21b700000
kernel config: https://syzkaller.appspot.com/x/.config?x=530c68bef4e2b8a8
dashboard link: https://syzkaller.appspot.com/bug?extid=5c943fe38e86d615cac2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1467313b700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=121b7cb9700000

The issue was bisected to:

commit 519f490db07e1a539490612f376487f61e48e39c
Author: Christian König <christia...@amd.com>
Date: Fri Mar 11 09:32:26 2022 +0000

dma-buf/sync-file: fix warning about fence containers

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1058277d700000
final oops: https://syzkaller.appspot.com/x/report.txt?x=1258277d700000
console output: https://syzkaller.appspot.com/x/log.txt?x=1458277d700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5c943f...@syzkaller.appspotmail.com
Fixes: 519f490db07e ("dma-buf/sync-file: fix warning about fence containers")

general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 PID: 3595 Comm: syz-executor814 Not tainted 5.17.0-next-20220328-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:dma_fence_array_first+0x78/0xb0 drivers/dma-buf/dma-fence-array.c:234
Code: 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 43 48 8b 9b 88 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 75 1b 4c 8b 23 e8 fa a9 e0 fc 4c 89 e0 5b 41 5c c3 45
RSP: 0018:ffffc90003a4fd48 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000010 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffffffff84980052 RDI: ffff888015c76388
RBP: ffff888015c76300 R08: 0000000000000000 R09: ffff888015c7633b
R10: ffffffff8498f6ba R11: 0000000000000000 R12: ffff888015c76300
R13: ffff888015c76690 R14: 00000000c0383e04 R15: 0000000020001840
FS: 0000555556872300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001528 CR3: 000000001e82f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__dma_fence_unwrap_array include/linux/dma-fence-unwrap.h:42 [inline]
dma_fence_unwrap_first include/linux/dma-fence-unwrap.h:57 [inline]
sync_file_ioctl_fence_info drivers/dma-buf/sync_file.c:414 [inline]
sync_file_ioctl+0x248/0x22c0 drivers/dma-buf/sync_file.c:477
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f6aae8951b9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffedd290238 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f6aae8951b9
RDX: 0000000020001840 RSI: 00000000c0383e04 RDI: 0000000000000007
RBP: 00007f6aae8591a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6aae859230
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dma_fence_array_first+0x78/0xb0 drivers/dma-buf/dma-fence-array.c:234
Code: 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 43 48 8b 9b 88 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 75 1b 4c 8b 23 e8 fa a9 e0 fc 4c 89 e0 5b 41 5c c3 45
RSP: 0018:ffffc90003a4fd48 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000010 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffffffff84980052 RDI: ffff888015c76388
RBP: ffff888015c76300 R08: 0000000000000000 R09: ffff888015c7633b
R10: ffffffff8498f6ba R11: 0000000000000000 R12: ffff888015c76300
R13: ffff888015c76690 R14: 00000000c0383e04 R15: 0000000020001840
FS: 0000555556872300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001528 CR3: 000000001e82f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 4 bytes skipped:
0: df 48 89 fisttps -0x77(%rax)
3: fa cli
4: 48 c1 ea 03 shr $0x3,%rdx
8: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
c: 75 43 jne 0x51
e: 48 8b 9b 88 00 00 00 mov 0x88(%rbx),%rbx
15: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
1c: fc ff df
1f: 48 89 da mov %rbx,%rdx
22: 48 c1 ea 03 shr $0x3,%rdx
* 26: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2a: 75 1b jne 0x47
2c: 4c 8b 23 mov (%rbx),%r12
2f: e8 fa a9 e0 fc callq 0xfce0aa2e
34: 4c 89 e0 mov %r12,%rax
37: 5b pop %rbx
38: 41 5c pop %r12
3a: c3 retq
3b: 45 rex.RB


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Pavel Skripkin]

On 3/30/22 00:23, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 8515d05bf6bc Add linux-next specific files for 20220328
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1694e21b700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=530c68bef4e2b8a8
> dashboard link: https://syzkaller.appspot.com/bug?extid=5c943fe38e86d615cac2
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1467313b700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=121b7cb9700000
>
> The issue was bisected to:
>
> commit 519f490db07e1a539490612f376487f61e48e39c
> Author: Christian König <christia...@amd.com>
> Date: Fri Mar 11 09:32:26 2022 +0000
>
> dma-buf/sync-file: fix warning about fence containers
>

There is ZERO_PTR dereference caused by passing 0 to krealloc_array().
Code should not try to reduce allocated memory area if index is equal to 0

#syz test:
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master




With regards,
Pavel Skripkin

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+5c943f...@syzkaller.appspotmail.com

Tested on:

commit: c2528a0c Add linux-next specific files for 20220329
git tree: linux-next
kernel config: https://syzkaller.appspot.com/x/.config?x=88d1370cc1f241e6

dashboard link: https://syzkaller.appspot.com/bug?extid=5c943fe38e86d615cac2
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=128372e7700000

Note: testing is done by a robot and is best-effort only.