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WARNING in v9fs_begin_writeback

Status: upstream: reported C repro on 2024/08/06 09:45
Subsystems: v9fs
[Documentation on labels]
Reported-by: syzbot+0b74d367d6e80661d6df@syzkaller.appspotmail.com
First crash: 660d, last: 16d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
75a89fc8-1c14-4085-9bb4-2a9fb663e99f assessment-security 💥 WARNING in v9fs_begin_writeback 2026/05/17 07:51 2026/05/17 07:51 2026/05/17 08:22 de5aae85e5f28e2fa1c7deefcc24fe286abe5140 failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32a8d5205daf7ef7ff3ad75c59ec41c1c53e5e53" "-s" "bzImage" "compile_commands.json"]: exit status 2 Root cause: ld.lld: error: undefined symbol: wcslen * * Restart config... * * * General architecture-dependent options * Kprobes (KPROBES) [N/y/?] n Optimize very unlikely/likely branches (JUMP_LABEL) [Y/n/?] y Static key selftest (STATIC_KEYS_SELFTEST) [N/y/?] n Static call selftest (STATIC_CALL_SELFTEST) [N/y/?] n Enable seccomp to safely execute untrusted bytecode (SECCOMP) [Y/n/?] y Show seccomp filter cache status in /proc/pid/seccomp_cache (SECCOMP_CACHE_DEBUG) [N/y/?] n Stack Protector buffer overflow detection (STACKPROTECTOR) [Y/n/?] y Strong Stack Protector (STACKPROTECTOR_STRONG) [Y/n/?] y Link Time Optimization (LTO) > 1. None (LTO_NONE) choice[1]: 1 Use Clang's Control Flow Integrity (CFI) (CFI_CLANG) [N/y/?] (NEW) Error in reading or end of file. Number of bits to use for ASLR of mmap base address (ARCH_MMAP_RND_BITS) [28] 28 Number of bits to use for ASLR of mmap base address for compatible applications (ARCH_MMAP_RND_COMPAT_BITS) [8] 8 MMU page size > 1. 4KiB pages (PAGE_SIZE_4KB) choice[1]: 1 Provide system calls for 32-bit time_t (COMPAT_32BIT_TIME) [Y/n/?] y Use a virtually-mapped stack (VMAP_STACK) [Y/n/?] y Support for randomizing kernel stack offset on syscall entry (RANDOMIZE_KSTACK_OFFSET) [Y/n/?] y Default state of kernel stack offset randomization (RANDOMIZE_KSTACK_OFFSET_DEFAULT) [N/y/?] n Locking event counts collection (LOCK_EVENT_COUNTS) [N/y/?] n * * Kernel hardening options * Randomize layout of sensitive kernel structures > 1. Disable structure layout randomization (RANDSTRUCT_NONE) 2. Fully randomize structure layout (RANDSTRUCT_FULL) (NEW) choice[1-2?]: Error in reading or end of file. * * Compile-time checks and compiler options * Debug information 1. Disable debug information (DEBUG_INFO_NONE) 2. Rely on the toolchain's implicit default DWARF version (DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT) > 3. Generate DWARF Version 4 debuginfo (DEBUG_INFO_DWARF4) 4. Generate DWARF Version 5 debuginfo (DEBUG_INFO_DWARF5) choice[1-4?]: 3 Reduce debugging information (DEBUG_INFO_REDUCED) [N/y/?] n Compressed Debug information > 1. Don't compress debug information (DEBUG_INFO_COMPRESSED_NONE) 2. Compress debugging information with zlib (DEBUG_INFO_COMPRESSED_ZLIB) 3. Compress debugging information with zstd (DEBUG_INFO_COMPRESSED_ZSTD) (NEW) choice[1-3?]: Error in reading or end of file. Produce split debuginfo in .dwo files (DEBUG_INFO_SPLIT) [N/y/?] n Generate BTF type information (DEBUG_INFO_BTF) [N/y/?] n Provide GDB scripts for kernel debugging (GDB_SCRIPTS) [N/y/?] n Warn for stack frames larger than (FRAME_WARN) [2048] 2048 Strip assembler-generated symbols during link (STRIP_ASM_SYMS) [N/y/?] n Install uapi headers to usr/include (HEADERS_INSTALL) [N/y/?] n Make section mismatch errors non-fatal (SECTION_MISMATCH_WARN_ONLY) [Y/n/?] y Force all function address 64B aligned (DEBUG_FORCE_FUNCTION_ALIGN_64B) [N/y/?] n Generate vmlinux.map file when linking (VMLINUX_MAP) [N/y/?] n Force weak per-cpu definitions (DEBUG_FORCE_WEAK_PER_CPU) [N/y/?] n In file included from /app/workdir/cache/src/43f7d94dc2c8df687f11164c4709470f1ccb03ad/net/socket.c:108: In file included from /app/workdir/cache/src/43f7d94dc2c8df687f11164c4709470f1ccb03ad/include/net/busy_poll.h:18: /app/workdir/cache/src/43f7d94dc2c8df687f11164c4709470f1ccb03ad/include/net/ip.h:472:14: warning: default initialization of an object of type 'typeof (rt->dst.expires)' (aka 'const unsigned long') leaves the object uninitialized [-Wdefault-const-init-var-unsafe] 472 | if (mtu && time_before(jiffies, rt->dst.expires)) | ^ /app/workdir/cache/src/43f7d94dc2c8df687f11164c4709470f1ccb03ad/include/linux/jiffies.h:138:26: note: expanded from macro 'time_before' 138 | #define time_before(a,b) time
2814e454-a94d-4597-98dc-32f49074c27c patching 💥 WARNING in v9fs_begin_writeback 2026/05/10 09:19 2026/05/10 13:05 2026/05/10 13:29 29233ece713919081e9069c2a18be92526041f39 reproducer did not crash
▶ ▼ Discussions (4)
Title Replies (including bot) Last reply
[syzbot] Monthly v9fs report (Oct 2025) 0 (1) 2025/10/20 11:38
[syzbot] Monthly v9fs report (Oct 2024) 0 (1) 2024/10/31 09:10
[syzbot] Monthly v9fs report (Aug 2024) 0 (1) 2024/08/29 13:20
[syzbot] [v9fs?] WARNING in v9fs_begin_writeback 26 (63) 2024/08/15 08:13
▶ ▼ Last patch testing requests (46)
Created Duration User Patch Repo Result
2026/05/08 19:45 18m retest repro upstream report log
2026/02/27 18:26 14m retest repro upstream report log
2025/12/19 17:07 14m retest repro upstream report log
2025/10/10 16:08 19m retest repro upstream report log
2025/08/01 15:03 37m retest repro upstream report log
2025/05/23 14:20 19m retest repro upstream report log
2025/03/14 13:31 16m retest repro upstream report log
2025/01/03 12:58 13m retest repro upstream report log
2024/10/25 12:16 16m retest repro upstream report log
2024/08/16 11:36 19m retest repro upstream report log
2024/08/15 08:13 20m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/15 03:00 19m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/15 02:31 18m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/14 10:26 24m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 OK log
2024/08/14 09:27 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/13 00:29 26m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/12 10:52 24m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/11 14:05 26m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/11 12:38 24m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/11 11:57 10m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/11 10:18 24m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/11 08:47 24m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/11 06:14 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/11 04:50 11m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/10 04:55 23m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/10 04:53 11m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/10 03:37 24m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/10 02:57 12m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/10 00:59 20m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 14:52 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 13:32 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 12:05 12m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/09 11:24 11m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/09 09:20 19m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 08:36 19m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 08:15 12m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/09 07:41 19m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 06:41 18m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 05:48 19m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/09 01:44 18m lizhi.xu@windriver.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/08 23:23 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/08 15:02 19m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/08 13:35 20m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/08 11:49 20m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log
2024/08/08 11:10 12m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 error
2024/08/06 11:35 20m eadavis@qq.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git c0ecd6388360 report log

Sample crash report:
------------[ cut here ]------------
folio expected an open fid inode->i_ino=23005ff
WARNING: CPU: 2 PID: 1155 at fs/9p/vfs_addr.c:39 v9fs_begin_writeback fs/9p/vfs_addr.c:39 [inline]
WARNING: CPU: 2 PID: 1155 at fs/9p/vfs_addr.c:39 v9fs_begin_writeback+0x210/0x280 fs/9p/vfs_addr.c:33
Modules linked in:
CPU: 2 UID: 0 PID: 1155 Comm: kworker/u32:9 Not tainted 6.11.0-rc1-syzkaller-00154-gc0ecd6388360 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: writeback wb_workfn (flush-9p-55)
RIP: 0010:v9fs_begin_writeback fs/9p/vfs_addr.c:39 [inline]
RIP: 0010:v9fs_begin_writeback+0x210/0x280 fs/9p/vfs_addr.c:33
Code: 00 fc ff df 48 8b 5b 48 48 8d 7b 40 48 89 fa 48 c1 ea 03 80 3c 02 00 75 66 48 8b 73 40 48 c7 c7 20 9a 8e 8b e8 51 4a 0d fe 90 <0f> 0b 90 90 e9 62 ff ff ff e8 32 2b a8 fe e9 51 ff ff ff e8 98 2a
RSP: 0018:ffffc9000610f480 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8880327a0670 RCX: ffffffff814cc379
RDX: ffff88802329a440 RSI: ffffffff814cc386 RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888012c4a408
R13: dffffc0000000000 R14: ffffc9000610f840 R15: ffff888012c4a658
FS:  0000000000000000(0000) GS:ffff88806b200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020001000 CR3: 0000000011d46000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 netfs_writepages+0x656/0xde0 fs/netfs/write_issue.c:534
 do_writepages+0x1a3/0x7f0 mm/page-writeback.c:2683
 __writeback_single_inode+0x163/0xf90 fs/fs-writeback.c:1651
 writeback_sb_inodes+0x611/0x1150 fs/fs-writeback.c:1947
 wb_writeback+0x199/0xb50 fs/fs-writeback.c:2127
 wb_do_writeback fs/fs-writeback.c:2274 [inline]
 wb_workfn+0x28d/0xf40 fs/fs-writeback.c:2314
 process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
 process_scheduled_works kernel/workqueue.c:3312 [inline]
 worker_thread+0x6c8/0xf20 kernel/workqueue.c:3390
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/08/02 11:35 upstream c0ecd6388360 1e9c4cf3 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in v9fs_begin_writeback
2024/08/02 09:42 upstream c0ecd6388360 1e9c4cf3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in v9fs_begin_writeback
* Struck through repros no longer work on HEAD.