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KFENCE: memory corruption in p9_req_put

Status: fixed on 2023/02/24 13:50
Subsystems: v9fs
[Documentation on labels]
Reported-by: syzbot+8f1060e2aaf8ca55220b@syzkaller.appspotmail.com
Fix commit: 26273ade77f5 9p: set req refcount to zero to avoid uninitialized usage
First crash: 526d, last: 524d
▶ ▼ Discussions (3)
Title Replies (including bot) Last reply
[PATCH v3] 9p/fd: set req refcount to zero to avoid uninitialized usage 4 (4) 2022/12/04 14:35
[PATCH] 9p: fix crash when transaction killed 16 (16) 2022/12/01 02:26
[PATCH v2] 9p/fd: set req refcount to zero to avoid uninitialized usage 3 (3) 2022/12/01 02:14

Sample crash report:
==================================================================
BUG: KFENCE: memory corruption in p9_fcall_fini net/9p/client.c:248 [inline]
BUG: KFENCE: memory corruption in p9_req_put net/9p/client.c:396 [inline]
BUG: KFENCE: memory corruption in p9_req_put+0x208/0x250 net/9p/client.c:390

Corrupted memory at 0xffff88823bd7c016 [ 0x00 . . . . . . . . . . . . . . . ] (in kfence-#189):
 p9_fcall_fini net/9p/client.c:248 [inline]
 p9_req_put net/9p/client.c:396 [inline]
 p9_req_put+0x208/0x250 net/9p/client.c:390
 p9_client_walk+0x247/0x540 net/9p/client.c:1165
 v9fs_vfs_lookup.part.0+0x143/0x5d0 fs/9p/vfs_inode.c:777
 v9fs_vfs_lookup+0x6d/0x90 fs/9p/vfs_inode.c:762
 __lookup_slow+0x24c/0x460 fs/namei.c:1685
 lookup_slow fs/namei.c:1702 [inline]
 walk_component+0x33f/0x5a0 fs/namei.c:1993
 lookup_last fs/namei.c:2450 [inline]
 path_lookupat+0x1ba/0x840 fs/namei.c:2474
 filename_lookup+0x1d2/0x590 fs/namei.c:2503
 vfs_statx+0x14c/0x430 fs/stat.c:229
 vfs_fstatat+0x90/0xb0 fs/stat.c:267
 vfs_stat include/linux/fs.h:3292 [inline]
 __do_sys_newstat+0x8b/0x110 fs/stat.c:410
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

kfence-#189: 0xffff88823bd7c000-0xffff88823bd7c015, size=22, cache=kmalloc-32

allocated by task 641 on cpu 0 at 2864.879249s:
 kmalloc include/linux/slab.h:558 [inline]
 p9_fcall_init+0x97/0x210 net/9p/client.c:228
 p9_tag_alloc+0x208/0x840 net/9p/client.c:293
 p9_client_prepare_req+0x177/0x590 net/9p/client.c:631
 p9_client_rpc+0x1a1/0xd70 net/9p/client.c:678
 p9_client_walk+0x1a0/0x540 net/9p/client.c:1152
 v9fs_vfs_lookup.part.0+0x143/0x5d0 fs/9p/vfs_inode.c:777
 v9fs_vfs_lookup+0x6d/0x90 fs/9p/vfs_inode.c:762
 __lookup_slow+0x24c/0x460 fs/namei.c:1685
 lookup_slow fs/namei.c:1702 [inline]
 walk_component+0x33f/0x5a0 fs/namei.c:1993
 lookup_last fs/namei.c:2450 [inline]
 path_lookupat+0x1ba/0x840 fs/namei.c:2474
 filename_lookup+0x1d2/0x590 fs/namei.c:2503
 vfs_statx+0x14c/0x430 fs/stat.c:229
 vfs_fstatat+0x90/0xb0 fs/stat.c:267
 vfs_stat include/linux/fs.h:3292 [inline]
 __do_sys_newstat+0x8b/0x110 fs/stat.c:410
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

freed by task 641 on cpu 0 at 2864.887801s:
 p9_fcall_fini net/9p/client.c:248 [inline]
 p9_req_put net/9p/client.c:396 [inline]
 p9_req_put+0x208/0x250 net/9p/client.c:390
 p9_client_walk+0x247/0x540 net/9p/client.c:1165
 v9fs_vfs_lookup.part.0+0x143/0x5d0 fs/9p/vfs_inode.c:777
 v9fs_vfs_lookup+0x6d/0x90 fs/9p/vfs_inode.c:762
 __lookup_slow+0x24c/0x460 fs/namei.c:1685
 lookup_slow fs/namei.c:1702 [inline]
 walk_component+0x33f/0x5a0 fs/namei.c:1993
 lookup_last fs/namei.c:2450 [inline]
 path_lookupat+0x1ba/0x840 fs/namei.c:2474
 filename_lookup+0x1d2/0x590 fs/namei.c:2503
 vfs_statx+0x14c/0x430 fs/stat.c:229
 vfs_fstatat+0x90/0xb0 fs/stat.c:267
 vfs_stat include/linux/fs.h:3292 [inline]
 __do_sys_newstat+0x8b/0x110 fs/stat.c:410
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

CPU: 0 PID: 641 Comm: syz-executor.2 Not tainted 6.1.0-rc5-syzkaller-00144-g84368d882b96 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2022/11/19 07:26 upstream 84368d882b96 5bb70014 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root KFENCE: memory corruption in p9_req_put
2022/11/16 13:34 upstream 59d0d52c30d4 3a127a31 .config console log report info ci-qemu-upstream-386 KFENCE: memory corruption in p9_req_put
* Struck through repros no longer work on HEAD.