[syzbot] KMSAN: uninit-value in p9pdu_readf

From: syzbot
Date: Sun Oct 10 2021 - 01:48:35 EST


Hello,

syzbot found the following issue on:

HEAD commit: c7f84f4e1147 kmsan: core: do not touch interrupts when ent..
git tree: https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=118e86a8b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=978f1b2d7a5aad3e
dashboard link: https://syzkaller.appspot.com/bug?extid=06472778c97ed94af66d
compiler: clang version 14.0.0 (git@xxxxxxxxxx:llvm/llvm-project.git 0996585c8e3b3d409494eb5f1cad714b9e1f7fb5), GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+06472778c97ed94af66d@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: uninit-value in p9pdu_vreadf net/9p/protocol.c:147 [inline]
BUG: KMSAN: uninit-value in p9pdu_readf+0x46cf/0x4fc0 net/9p/protocol.c:526
p9pdu_vreadf net/9p/protocol.c:147 [inline]
p9pdu_readf+0x46cf/0x4fc0 net/9p/protocol.c:526
p9pdu_vreadf net/9p/protocol.c:198 [inline]
p9pdu_readf+0x2080/0x4fc0 net/9p/protocol.c:526
p9_client_stat+0x2b3/0x710 net/9p/client.c:1724
v9fs_mount+0xc14/0x12c0 fs/9p/vfs_super.c:170
legacy_get_tree+0x163/0x2e0 fs/fs_context.c:610
vfs_get_tree+0xd8/0x5d0 fs/super.c:1498
do_new_mount+0x7bc/0x1680 fs/namespace.c:2988
path_mount+0x106f/0x2960 fs/namespace.c:3318
do_mount fs/namespace.c:3331 [inline]
__do_sys_mount fs/namespace.c:3539 [inline]
__se_sys_mount+0x8eb/0xa10 fs/namespace.c:3516
__ia32_sys_mount+0x157/0x1b0 fs/namespace.c:3516
do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
__do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Local variable ----ecode@p9_check_errors created at:
p9_check_errors+0x68/0xb90 net/9p/client.c:506
p9_client_rpc+0xd90/0x1410 net/9p/client.c:801
=====================================================
Kernel panic - not syncing: panic_on_kmsan set ...
CPU: 0 PID: 31201 Comm: syz-executor.3 Tainted: G B W 5.15.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1ff/0x28e lib/dump_stack.c:106
dump_stack+0x25/0x28 lib/dump_stack.c:113
panic+0x44f/0xdeb kernel/panic.c:232
kmsan_report+0x2ee/0x300 mm/kmsan/report.c:168
__msan_warning+0xa9/0xf0 mm/kmsan/instrumentation.c:199
p9pdu_vreadf net/9p/protocol.c:147 [inline]
p9pdu_readf+0x46cf/0x4fc0 net/9p/protocol.c:526
p9pdu_vreadf net/9p/protocol.c:198 [inline]
p9pdu_readf+0x2080/0x4fc0 net/9p/protocol.c:526
p9_client_stat+0x2b3/0x710 net/9p/client.c:1724
v9fs_mount+0xc14/0x12c0 fs/9p/vfs_super.c:170
legacy_get_tree+0x163/0x2e0 fs/fs_context.c:610
vfs_get_tree+0xd8/0x5d0 fs/super.c:1498
do_new_mount+0x7bc/0x1680 fs/namespace.c:2988
path_mount+0x106f/0x2960 fs/namespace.c:3318
do_mount fs/namespace.c:3331 [inline]
__do_sys_mount fs/namespace.c:3539 [inline]
__se_sys_mount+0x8eb/0xa10 fs/namespace.c:3516
__ia32_sys_mount+0x157/0x1b0 fs/namespace.c:3516
do_syscall_32_irqs_on arch/x86/entry/common.c:114 [inline]
__do_fast_syscall_32+0x96/0xf0 arch/x86/entry/common.c:180
do_fast_syscall_32+0x34/0x70 arch/x86/entry/common.c:205
do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:248
entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf6ef3549
Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00
RSP: 002b:00000000f44ed5fc EFLAGS: 00000296 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000020000000
RDX: 0000000020000140 RSI: 0000000000000000 RDI: 0000000020000580
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..
----------------
Code disassembly (best guess):
0: 03 74 c0 01 add 0x1(%rax,%rax,8),%esi
4: 10 05 03 74 b8 01 adc %al,0x1b87403(%rip) # 0x1b8740d
a: 10 06 adc %al,(%rsi)
c: 03 74 b4 01 add 0x1(%rsp,%rsi,4),%esi
10: 10 07 adc %al,(%rdi)
12: 03 74 b0 01 add 0x1(%rax,%rsi,4),%esi
16: 10 08 adc %cl,(%rax)
18: 03 74 d8 01 add 0x1(%rax,%rbx,8),%esi
1c: 00 00 add %al,(%rax)
1e: 00 00 add %al,(%rax)
20: 00 51 52 add %dl,0x52(%rcx)
23: 55 push %rbp
24: 89 e5 mov %esp,%ebp
26: 0f 34 sysenter
28: cd 80 int $0x80
* 2a: 5d pop %rbp <-- trapping instruction
2b: 5a pop %rdx
2c: 59 pop %rcx
2d: c3 retq
2e: 90 nop
2f: 90 nop
30: 90 nop
31: 90 nop
32: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
39: 00 00 00
3c: 0f .byte 0xf
3d: 1f (bad)
3e: 44 rex.R


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