On Sat, 14 Mar 2020 07:37:13 +0100, syzbot wrote:

Hello,

syzbot found the following crash on:

HEAD commit: 30bb5572 Merge tag 'ktest-v5.6' of git://git.kernel.org/pu.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=15d300b1e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=a5295e161cd85b82 dashboard link: https://syzkaller.appspot.com/bug?extid=8b0e78e390d1715b0f4e compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11a57709e00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13de9e91e00000

The bug was bisected to:

commit 271213ef4d0d3a3b80d4cf95c5f2bebb5643e666 Author: Takashi Iwai tiwai@suse.de Date: Tue Dec 10 06:34:50 2019 +0000

ALSA: pcxhr: Support PCM sync_stop

This must be a false-positive. The config doesn't contain CONFIG_SND_PCXHR and this commit changes only sound/pci/pcxhr.c.

thanks,

Takashi

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1566b08de00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=1766b08de00000 console output: https://syzkaller.appspot.com/x/log.txt?x=1366b08de00000

IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+8b0e78e390d1715b0f4e@syzkaller.appspotmail.com Fixes: 271213ef4d0d ("ALSA: pcxhr: Support PCM sync_stop")

BUG: kernel NULL pointer dereference, address: 0000000000000086 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page PGD a27fa067 P4D a27fa067 PUD a2185067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN CPU: 1 PID: 9168 Comm: syz-executor418 Not tainted 5.6.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:0x86 Code: Bad RIP value. RSP: 0018:ffffc90002c9f998 EFLAGS: 00010086 RAX: ffffc90002c9f9c8 RBX: fffffe0000000000 RCX: ffff8880a31b6280 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: 0000000000000ec0 R08: ffffffff839888d3 R09: ffffffff811c7d9a R10: ffff8880a31b6280 R11: 0000000000000002 R12: dffffc0000000000 R13: fffffe0000000ec8 R14: ffffffff880016f0 R15: fffffe0000000ecb FS: 0000000000981880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000005c CR3: 00000000986d2000 CR4: 00000000001426e0 Call Trace: Modules linked in: CR2: 0000000000000086 ---[ end trace 7c78bc94cfc0a37d ]--- RIP: 0010:0x86 Code: Bad RIP value. RSP: 0018:ffffc90002c9f998 EFLAGS: 00010086 RAX: ffffc90002c9f9c8 RBX: fffffe0000000000 RCX: ffff8880a31b6280 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 RBP: 0000000000000ec0 R08: ffffffff839888d3 R09: ffffffff811c7d9a R10: ffff8880a31b6280 R11: 0000000000000002 R12: dffffc0000000000 R13: fffffe0000000ec8 R14: ffffffff880016f0 R15: fffffe0000000ecb FS: 0000000000981880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000005c CR3: 00000000986d2000 CR4: 00000000001426e0

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