syzbot


kernel BUG in jffs2_start_garbage_collect_thread

Status: upstream: reported C repro on 2024/04/08 05:37
Subsystems: jffs2
[Documentation on labels]
Reported-by: syzbot+61a9d95630970eece39d@syzkaller.appspotmail.com
First crash: 795d, last: 646d
Cause bisection: introduced by (bisect log) :
commit 9c8ad7a2ff0bfe58f019ec0abc1fb965114dde7d
Author: David Howells <dhowells@redhat.com>
Date: Thu May 16 11:52:27 2019 +0000

  uapi, x86: Fix the syscall numbering of the mount API syscalls [ver #2]

Crash: KASAN: use-after-free Read in jffs2_garbage_collect_pass (log)
Repro: C syz .config
  
Fix bisection: failed (error log, bisect log)
  
✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision Error
073a96c1-d58e-492d-82de-3216c424bba1 assessment-security 💥 kernel BUG in jffs2_start_garbage_collect_thread 2026/06/09 18:24 2026/06/09 18:24 2026/06/09 18:41 c36c07f6c1f2230a36374cbd22235f635e8f9284 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/26ff704851aeea83da39a9e71f6b6bdce5da9865" "-s" "bzImage" "compile_commands.json"]: exit status 2 Root cause: include/linux/thread_info.h:244:4: error: call to '__bad_copy_from' declared with 'error' attribute: copy source size is too small drivers/nvme/target/fc.c:151:2: warning: 'counted_by' should not be applied to an array with element of unknown size because 'struct nvmet_fc_fcp_iod' is a struct type with a flexible array member. This will be an error in a future compiler version [-Wbounds-safety-counted-by-elt-type-unknown-size] * * 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 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 * * Memory initialization * Initialize kernel stack variables at function entry 1. no automatic stack variable initialization (weakest) (INIT_STACK_NONE) 2. pattern-init everything (strongest) (INIT_STACK_ALL_PATTERN) > 3. zero-init everything (strongest and safest) (INIT_STACK_ALL_ZERO) choice[1-3?]: 3 Enable heap memory zeroing on allocation by default (INIT_ON_ALLOC_DEFAULT_ON) [Y/n/?] y Enable heap memory zeroing on free by default (INIT_ON_FREE_DEFAULT_ON) [N/y/?] n Enable register zeroing on function exit (ZERO_CALL_USED_REGS) [N/y/?] (NEW) Error in reading or end of file. * * 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 typeinfo (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/
0e86d8dd-49cb-4427-98f4-bb1718dfd422 assessment-security 💥 kernel BUG in jffs2_start_garbage_collect_thread 2026/06/02 15:33 2026/06/02 15:33 2026/06/02 15:56 62fe15281f5011cd203d8845b8767b10e7443aa5 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/26ff704851aeea83da39a9e71f6b6bdce5da9865" "-s" "bzImage" "compile_commands.json"]: exit status 2 Root cause: include/linux/thread_info.h:244:4: error: call to '__bad_copy_from' declared with 'error' attribute: copy source size is too small drivers/nvme/target/fc.c:151:2: warning: 'counted_by' should not be applied to an array with element of unknown size because 'struct nvmet_fc_fcp_iod' is a struct type with a flexible array member. This will be an error in a future compiler version [-Wbounds-safety-counted-by-elt-type-unknown-size] * * 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 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 * * Memory initialization * Initialize kernel stack variables at function entry 1. no automatic stack variable initialization (weakest) (INIT_STACK_NONE) 2. pattern-init everything (strongest) (INIT_STACK_ALL_PATTERN) > 3. zero-init everything (strongest and safest) (INIT_STACK_ALL_ZERO) choice[1-3?]: 3 Enable heap memory zeroing on allocation by default (INIT_ON_ALLOC_DEFAULT_ON) [Y/n/?] y Enable heap memory zeroing on free by default (INIT_ON_FREE_DEFAULT_ON) [N/y/?] n Enable register zeroing on function exit (ZERO_CALL_USED_REGS) [N/y/?] (NEW) Error in reading or end of file. * * 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 typeinfo (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/
920d0240-8817-4816-83b0-d0c49327ad48 assessment-security 💥 kernel BUG in jffs2_start_garbage_collect_thread 2026/05/25 18:59 2026/05/25 18:59 2026/05/25 19:25 c69befb30ac10e158cc9d1557b508ee3f0eca1de 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/26ff704851aeea83da39a9e71f6b6bdce5da9865" "-s" "bzImage" "compile_commands.json"]: exit status 2 Root cause: include/linux/thread_info.h:244:4: error: call to '__bad_copy_from' declared with 'error' attribute: copy source size is too small drivers/nvme/target/fc.c:151:2: warning: 'counted_by' should not be applied to an array with element of unknown size because 'struct nvmet_fc_fcp_iod' is a struct type with a flexible array member. This will be an error in a future compiler version [-Wbounds-safety-counted-by-elt-type-unknown-size] * * 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 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 * * Memory initialization * Initialize kernel stack variables at function entry 1. no automatic stack variable initialization (weakest) (INIT_STACK_NONE) 2. pattern-init everything (strongest) (INIT_STACK_ALL_PATTERN) > 3. zero-init everything (strongest and safest) (INIT_STACK_ALL_ZERO) choice[1-3?]: 3 Enable heap memory zeroing on allocation by default (INIT_ON_ALLOC_DEFAULT_ON) [Y/n/?] y Enable heap memory zeroing on free by default (INIT_ON_FREE_DEFAULT_ON) [N/y/?] n Enable register zeroing on function exit (ZERO_CALL_USED_REGS) [N/y/?] (NEW) Error in reading or end of file. * * 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 typeinfo (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/
Discussions (5)
Title Replies (including bot) Last reply
[PATCH 1/3] jffs2: always stop garbage collection thread on unmount 3 (3) 2026/05/01 11:02
[syzbot] [jffs2?] kernel BUG in jffs2_start_garbage_collect_thread 0 (2) 2026/04/30 23:58
[syzbot] Monthly jffs2 report (Sep 2024) 0 (1) 2024/09/09 08:12
[syzbot] Monthly jffs2 report (Aug 2024) 0 (1) 2024/08/06 12:39
[syzbot] Monthly jffs2 report (May 2024) 0 (1) 2024/05/16 12:44
Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/05/25 01:31 56m retest repro upstream log
2026/04/30 23:58 26m tristmd@gmail.com patch upstream OK log
2026/02/28 10:14 11m retest repro upstream report log
2025/12/20 08:45 14m retest repro upstream report log
2025/10/11 00:34 13m retest repro upstream report log
2025/07/31 15:48 1h46m retest repro upstream report log
2025/05/21 05:03 14m retest repro upstream report log
2025/03/04 06:39 15m retest repro upstream report log
2024/12/24 01:45 12m retest repro upstream report log
2024/04/27 10:21 10m retest repro upstream report log
Fix bisection attempts (5)
Created Duration User Patch Repo Result
2024/10/14 23:45 0m bisect fix upstream error job log
2024/09/03 05:56 1h26m bisect fix upstream OK (0) job log log
2024/07/29 22:57 2h31m bisect fix upstream OK (0) job log log
2024/06/22 17:23 2h19m bisect fix upstream OK (0) job log log
2024/05/16 04:15 1h20m bisect fix upstream OK (0) job log log

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/jffs2/background.c:40!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 0 PID: 5060 Comm: syz-executor108 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:jffs2_start_garbage_collect_thread+0x1f5/0x200 fs/jffs2/background.c:40
Code: 03 ff e9 1b ff ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 64 ff ff ff 48 89 df e8 76 78 03 ff e9 57 ff ff ff e8 9c 77 a3 fe 90 <0f> 0b 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000422fd00 EFLAGS: 00010293
RAX: ffffffff82f17cb4 RBX: ffff8880240a6018 RCX: ffff8880242b5a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880240a6000
RBP: 0000000000000000 R08: ffffffff82f1c1c9 R09: 1ffff92000845f94
R10: dffffc0000000000 R11: fffff52000845f95 R12: ffff8880240a6000
R13: dffffc0000000000 R14: ffff8880240a6000 R15: ffff88802e7774f8
FS:  000055559415a380(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f54dacad0d0 CR3: 000000007aeec000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 jffs2_do_remount_fs+0x15b/0x1d0 fs/jffs2/fs.c:415
 reconfigure_super+0x445/0x880 fs/super.c:1071
 vfs_cmd_reconfigure fs/fsopen.c:267 [inline]
 vfs_fsconfig_locked fs/fsopen.c:296 [inline]
 __do_sys_fsconfig fs/fsopen.c:476 [inline]
 __se_sys_fsconfig+0xab5/0xec0 fs/fsopen.c:349
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f54dac35cf9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc9713c8d8 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f54dac35cf9
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000003
RBP: 0000000000010305 R08: 0000000000000000 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc9713c8ec
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:jffs2_start_garbage_collect_thread+0x1f5/0x200 fs/jffs2/background.c:40
Code: 03 ff e9 1b ff ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 64 ff ff ff 48 89 df e8 76 78 03 ff e9 57 ff ff ff e8 9c 77 a3 fe 90 <0f> 0b 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000422fd00 EFLAGS: 00010293
RAX: ffffffff82f17cb4 RBX: ffff8880240a6018 RCX: ffff8880242b5a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880240a6000
RBP: 0000000000000000 R08: ffffffff82f1c1c9 R09: 1ffff92000845f94
R10: dffffc0000000000 R11: fffff52000845f95 R12: ffff8880240a6000
R13: dffffc0000000000 R14: ffff8880240a6000 R15: ffff88802e7774f8
FS:  000055559415a380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc9713c7d8 CR3: 000000007aeec000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/04/07 10:51 upstream fe46a7dd189e ca620dd8 .config strace log report syz C [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in jffs2_start_garbage_collect_thread
2024/04/13 06:20 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in jffs2_start_garbage_collect_thread
2024/04/11 15:05 upstream fe46a7dd189e 95ed9ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in jffs2_start_garbage_collect_thread
* Struck through repros no longer work on HEAD.