| Message ID | 20241104020542.2603607-1-leo.lilong@huawei.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 7b0033dbc48340a1c1c3f12448ba17d6587ca092 |
| Headers | show |
| Series | [f2fs-dev,v2] f2fs: fix race in concurrent f2fs_stop_gc_thread | expand |
On 2024/11/4 10:05, Long Li wrote: > In my test case, concurrent calls to f2fs shutdown report the following > stack trace: > > Oops: general protection fault, probably for non-canonical address 0xc6cfff63bb5513fc: 0000 [#1] PREEMPT SMP PTI > CPU: 0 UID: 0 PID: 678 Comm: f2fs_rep_shutdo Not tainted 6.12.0-rc5-next-20241029-g6fb2fa9805c5-dirty #85 > Call Trace: > <TASK> > ? show_regs+0x8b/0xa0 > ? __die_body+0x26/0xa0 > ? die_addr+0x54/0x90 > ? exc_general_protection+0x24b/0x5c0 > ? asm_exc_general_protection+0x26/0x30 > ? kthread_stop+0x46/0x390 > f2fs_stop_gc_thread+0x6c/0x110 > f2fs_do_shutdown+0x309/0x3a0 > f2fs_ioc_shutdown+0x150/0x1c0 > __f2fs_ioctl+0xffd/0x2ac0 > f2fs_ioctl+0x76/0xe0 > vfs_ioctl+0x23/0x60 > __x64_sys_ioctl+0xce/0xf0 > x64_sys_call+0x2b1b/0x4540 > do_syscall_64+0xa7/0x240 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > > The root cause is a race condition in f2fs_stop_gc_thread() called from > different f2fs shutdown paths: > > [CPU0] [CPU1] > ---------------------- ----------------------- > f2fs_stop_gc_thread f2fs_stop_gc_thread > gc_th = sbi->gc_thread > gc_th = sbi->gc_thread > kfree(gc_th) > sbi->gc_thread = NULL > < gc_th != NULL > > kthread_stop(gc_th->f2fs_gc_task) //UAF > > The commit c7f114d864ac ("f2fs: fix to avoid use-after-free in > f2fs_stop_gc_thread()") attempted to fix this issue by using a read > semaphore to prevent races between shutdown and remount threads, but > it fails to prevent all race conditions. > > Fix it by converting to write lock of s_umount in f2fs_do_shutdown(). > > Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") > Signed-off-by: Long Li <leo.lilong@huawei.com> Reviewed-by: Chao Yu <chao@kernel.org> Thanks,
Hello: This patch was applied to jaegeuk/f2fs.git (dev) by Jaegeuk Kim <jaegeuk@kernel.org>: On Mon, 4 Nov 2024 10:05:42 +0800 you wrote: > In my test case, concurrent calls to f2fs shutdown report the following > stack trace: > > Oops: general protection fault, probably for non-canonical address 0xc6cfff63bb5513fc: 0000 [#1] PREEMPT SMP PTI > CPU: 0 UID: 0 PID: 678 Comm: f2fs_rep_shutdo Not tainted 6.12.0-rc5-next-20241029-g6fb2fa9805c5-dirty #85 > Call Trace: > <TASK> > ? show_regs+0x8b/0xa0 > ? __die_body+0x26/0xa0 > ? die_addr+0x54/0x90 > ? exc_general_protection+0x24b/0x5c0 > ? asm_exc_general_protection+0x26/0x30 > ? kthread_stop+0x46/0x390 > f2fs_stop_gc_thread+0x6c/0x110 > f2fs_do_shutdown+0x309/0x3a0 > f2fs_ioc_shutdown+0x150/0x1c0 > __f2fs_ioctl+0xffd/0x2ac0 > f2fs_ioctl+0x76/0xe0 > vfs_ioctl+0x23/0x60 > __x64_sys_ioctl+0xce/0xf0 > x64_sys_call+0x2b1b/0x4540 > do_syscall_64+0xa7/0x240 > entry_SYSCALL_64_after_hwframe+0x76/0x7e > > [...] Here is the summary with links: - [f2fs-dev,v2] f2fs: fix race in concurrent f2fs_stop_gc_thread https://git.kernel.org/jaegeuk/f2fs/c/7b0033dbc483 You are awesome, thank you!
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 75a8b22da664..703cfccc6b7e 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2365,9 +2365,12 @@ int f2fs_do_shutdown(struct f2fs_sb_info *sbi, unsigned int flag, if (readonly) goto out; - /* grab sb->s_umount to avoid racing w/ remount() */ + /* + * grab sb->s_umount to avoid racing w/ remount() and other shutdown + * paths. + */ if (need_lock) - down_read(&sbi->sb->s_umount); + down_write(&sbi->sb->s_umount); f2fs_stop_gc_thread(sbi); f2fs_stop_discard_thread(sbi); @@ -2376,7 +2379,7 @@ int f2fs_do_shutdown(struct f2fs_sb_info *sbi, unsigned int flag, clear_opt(sbi, DISCARD); if (need_lock) - up_read(&sbi->sb->s_umount); + up_write(&sbi->sb->s_umount); f2fs_update_time(sbi, REQ_TIME); out:
In my test case, concurrent calls to f2fs shutdown report the following stack trace: Oops: general protection fault, probably for non-canonical address 0xc6cfff63bb5513fc: 0000 [#1] PREEMPT SMP PTI CPU: 0 UID: 0 PID: 678 Comm: f2fs_rep_shutdo Not tainted 6.12.0-rc5-next-20241029-g6fb2fa9805c5-dirty #85 Call Trace: <TASK> ? show_regs+0x8b/0xa0 ? __die_body+0x26/0xa0 ? die_addr+0x54/0x90 ? exc_general_protection+0x24b/0x5c0 ? asm_exc_general_protection+0x26/0x30 ? kthread_stop+0x46/0x390 f2fs_stop_gc_thread+0x6c/0x110 f2fs_do_shutdown+0x309/0x3a0 f2fs_ioc_shutdown+0x150/0x1c0 __f2fs_ioctl+0xffd/0x2ac0 f2fs_ioctl+0x76/0xe0 vfs_ioctl+0x23/0x60 __x64_sys_ioctl+0xce/0xf0 x64_sys_call+0x2b1b/0x4540 do_syscall_64+0xa7/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e The root cause is a race condition in f2fs_stop_gc_thread() called from different f2fs shutdown paths: [CPU0] [CPU1] ---------------------- ----------------------- f2fs_stop_gc_thread f2fs_stop_gc_thread gc_th = sbi->gc_thread gc_th = sbi->gc_thread kfree(gc_th) sbi->gc_thread = NULL < gc_th != NULL > kthread_stop(gc_th->f2fs_gc_task) //UAF The commit c7f114d864ac ("f2fs: fix to avoid use-after-free in f2fs_stop_gc_thread()") attempted to fix this issue by using a read semaphore to prevent races between shutdown and remount threads, but it fails to prevent all race conditions. Fix it by converting to write lock of s_umount in f2fs_do_shutdown(). Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") Signed-off-by: Long Li <leo.lilong@huawei.com> --- fs/f2fs/file.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)