| Message ID | 20240725020841.894814-1-chao@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [f2fs-dev] f2fs: fix to avoid use-after-free in f2fs_stop_gc_thread() | expand |
On 07/25, Chao Yu wrote: > syzbot reports a f2fs bug as below: > > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 > print_report+0xe8/0x550 mm/kasan/report.c:491 > kasan_report+0x143/0x180 mm/kasan/report.c:601 > kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 > instrument_atomic_read_write include/linux/instrumented.h:96 [inline] > atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] > __refcount_add include/linux/refcount.h:184 [inline] > __refcount_inc include/linux/refcount.h:241 [inline] > refcount_inc include/linux/refcount.h:258 [inline] > get_task_struct include/linux/sched/task.h:118 [inline] > kthread_stop+0xca/0x630 kernel/kthread.c:704 > f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:210 > f2fs_do_shutdown+0x192/0x540 fs/f2fs/file.c:2283 > f2fs_ioc_shutdown fs/f2fs/file.c:2325 [inline] > __f2fs_ioctl+0x443a/0xbe60 fs/f2fs/file.c:4325 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:907 [inline] > __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > The root cause is below race condition, it may cause use-after-free > issue in sbi->gc_th pointer. > > - remount > - f2fs_remount > - f2fs_stop_gc_thread > - kfree(gc_th) > - f2fs_ioc_shutdown > - f2fs_do_shutdown > - f2fs_stop_gc_thread > - kthread_stop(gc_th->f2fs_gc_task) > > We will call f2fs_do_shutdown() in two paths: > - for f2fs_ioc_shutdown() path, we should grab sb->s_umount semaphore > for fixing. > - for f2fs_shutdown() path, it's safe since caller has already grabbed > sb->s_umount semaphore. > > Reported-by: syzbot+1a8e2b31f2ac9bd3d148@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/linux-f2fs-devel/0000000000005c7ccb061e032b9b@google.com > Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") > Signed-off-by: Chao Yu <chao@kernel.org> > --- > fs/f2fs/file.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 7a37f2b393b9..62d72da25754 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -2388,7 +2388,10 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg) > } > } > > + /* grab sb->s_umount to avoid racing w/ remount() */ > + down_read(&sbi->sb->s_umount); Is this safe for freeze_bdev()? > ret = f2fs_do_shutdown(sbi, in, readonly); > + up_read(&sbi->sb->s_umount); > > if (need_drop) > mnt_drop_write_file(filp); > -- > 2.40.1
On 07/27, Jaegeuk Kim wrote: > On 07/25, Chao Yu wrote: > > syzbot reports a f2fs bug as below: > > > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 > > print_report+0xe8/0x550 mm/kasan/report.c:491 > > kasan_report+0x143/0x180 mm/kasan/report.c:601 > > kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 > > instrument_atomic_read_write include/linux/instrumented.h:96 [inline] > > atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] > > __refcount_add include/linux/refcount.h:184 [inline] > > __refcount_inc include/linux/refcount.h:241 [inline] > > refcount_inc include/linux/refcount.h:258 [inline] > > get_task_struct include/linux/sched/task.h:118 [inline] > > kthread_stop+0xca/0x630 kernel/kthread.c:704 > > f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:210 > > f2fs_do_shutdown+0x192/0x540 fs/f2fs/file.c:2283 > > f2fs_ioc_shutdown fs/f2fs/file.c:2325 [inline] > > __f2fs_ioctl+0x443a/0xbe60 fs/f2fs/file.c:4325 > > vfs_ioctl fs/ioctl.c:51 [inline] > > __do_sys_ioctl fs/ioctl.c:907 [inline] > > __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 > > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > > do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 > > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > > > The root cause is below race condition, it may cause use-after-free > > issue in sbi->gc_th pointer. > > > > - remount > > - f2fs_remount > > - f2fs_stop_gc_thread > > - kfree(gc_th) > > - f2fs_ioc_shutdown > > - f2fs_do_shutdown > > - f2fs_stop_gc_thread > > - kthread_stop(gc_th->f2fs_gc_task) > > > > We will call f2fs_do_shutdown() in two paths: > > - for f2fs_ioc_shutdown() path, we should grab sb->s_umount semaphore > > for fixing. > > - for f2fs_shutdown() path, it's safe since caller has already grabbed > > sb->s_umount semaphore. > > > > Reported-by: syzbot+1a8e2b31f2ac9bd3d148@syzkaller.appspotmail.com > > Closes: https://lore.kernel.org/linux-f2fs-devel/0000000000005c7ccb061e032b9b@google.com > > Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") > > Signed-off-by: Chao Yu <chao@kernel.org> > > --- > > fs/f2fs/file.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > > index 7a37f2b393b9..62d72da25754 100644 > > --- a/fs/f2fs/file.c > > +++ b/fs/f2fs/file.c > > @@ -2388,7 +2388,10 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg) > > } > > } > > > > + /* grab sb->s_umount to avoid racing w/ remount() */ > > + down_read(&sbi->sb->s_umount); > > Is this safe for freeze_bdev()? bdev_freeze -> fs_bdev_freeze -> get_bdev_super -> bdev_super_lock(bdev, true) -> super_lock(sb, true) -> __super_lock(sb, true) -> down_write(s_umount) > > > ret = f2fs_do_shutdown(sbi, in, readonly); > > + up_read(&sbi->sb->s_umount); > > > > if (need_drop) > > mnt_drop_write_file(filp); > > -- > > 2.40.1
On 2024/7/27 23:27, Jaegeuk Kim wrote: > On 07/27, Jaegeuk Kim wrote: >> On 07/25, Chao Yu wrote: >>> syzbot reports a f2fs bug as below: >>> >>> __dump_stack lib/dump_stack.c:88 [inline] >>> dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 >>> print_report+0xe8/0x550 mm/kasan/report.c:491 >>> kasan_report+0x143/0x180 mm/kasan/report.c:601 >>> kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 >>> instrument_atomic_read_write include/linux/instrumented.h:96 [inline] >>> atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] >>> __refcount_add include/linux/refcount.h:184 [inline] >>> __refcount_inc include/linux/refcount.h:241 [inline] >>> refcount_inc include/linux/refcount.h:258 [inline] >>> get_task_struct include/linux/sched/task.h:118 [inline] >>> kthread_stop+0xca/0x630 kernel/kthread.c:704 >>> f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:210 >>> f2fs_do_shutdown+0x192/0x540 fs/f2fs/file.c:2283 >>> f2fs_ioc_shutdown fs/f2fs/file.c:2325 [inline] >>> __f2fs_ioctl+0x443a/0xbe60 fs/f2fs/file.c:4325 >>> vfs_ioctl fs/ioctl.c:51 [inline] >>> __do_sys_ioctl fs/ioctl.c:907 [inline] >>> __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 >>> do_syscall_x64 arch/x86/entry/common.c:52 [inline] >>> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 >>> entry_SYSCALL_64_after_hwframe+0x77/0x7f >>> >>> The root cause is below race condition, it may cause use-after-free >>> issue in sbi->gc_th pointer. >>> >>> - remount >>> - f2fs_remount >>> - f2fs_stop_gc_thread >>> - kfree(gc_th) >>> - f2fs_ioc_shutdown >>> - f2fs_do_shutdown >>> - f2fs_stop_gc_thread >>> - kthread_stop(gc_th->f2fs_gc_task) >>> >>> We will call f2fs_do_shutdown() in two paths: >>> - for f2fs_ioc_shutdown() path, we should grab sb->s_umount semaphore >>> for fixing. >>> - for f2fs_shutdown() path, it's safe since caller has already grabbed >>> sb->s_umount semaphore. >>> >>> Reported-by: syzbot+1a8e2b31f2ac9bd3d148@syzkaller.appspotmail.com >>> Closes: https://lore.kernel.org/linux-f2fs-devel/0000000000005c7ccb061e032b9b@google.com >>> Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") >>> Signed-off-by: Chao Yu <chao@kernel.org> >>> --- >>> fs/f2fs/file.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>> index 7a37f2b393b9..62d72da25754 100644 >>> --- a/fs/f2fs/file.c >>> +++ b/fs/f2fs/file.c >>> @@ -2388,7 +2388,10 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg) >>> } >>> } >>> >>> + /* grab sb->s_umount to avoid racing w/ remount() */ >>> + down_read(&sbi->sb->s_umount); >> >> Is this safe for freeze_bdev()? > > bdev_freeze > -> fs_bdev_freeze > -> get_bdev_super > -> bdev_super_lock(bdev, true) > -> super_lock(sb, true) > -> __super_lock(sb, true) > -> down_write(s_umount) Oops, let me check this. Thanks, > >> >>> ret = f2fs_do_shutdown(sbi, in, readonly); >>> + up_read(&sbi->sb->s_umount); >>> >>> if (need_drop) >>> mnt_drop_write_file(filp); >>> -- >>> 2.40.1
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 7a37f2b393b9..62d72da25754 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2388,7 +2388,10 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg) } } + /* grab sb->s_umount to avoid racing w/ remount() */ + down_read(&sbi->sb->s_umount); ret = f2fs_do_shutdown(sbi, in, readonly); + up_read(&sbi->sb->s_umount); if (need_drop) mnt_drop_write_file(filp);
syzbot reports a f2fs bug as below: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 print_report+0xe8/0x550 mm/kasan/report.c:491 kasan_report+0x143/0x180 mm/kasan/report.c:601 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189 instrument_atomic_read_write include/linux/instrumented.h:96 [inline] atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline] __refcount_add include/linux/refcount.h:184 [inline] __refcount_inc include/linux/refcount.h:241 [inline] refcount_inc include/linux/refcount.h:258 [inline] get_task_struct include/linux/sched/task.h:118 [inline] kthread_stop+0xca/0x630 kernel/kthread.c:704 f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:210 f2fs_do_shutdown+0x192/0x540 fs/f2fs/file.c:2283 f2fs_ioc_shutdown fs/f2fs/file.c:2325 [inline] __f2fs_ioctl+0x443a/0xbe60 fs/f2fs/file.c:4325 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f The root cause is below race condition, it may cause use-after-free issue in sbi->gc_th pointer. - remount - f2fs_remount - f2fs_stop_gc_thread - kfree(gc_th) - f2fs_ioc_shutdown - f2fs_do_shutdown - f2fs_stop_gc_thread - kthread_stop(gc_th->f2fs_gc_task) We will call f2fs_do_shutdown() in two paths: - for f2fs_ioc_shutdown() path, we should grab sb->s_umount semaphore for fixing. - for f2fs_shutdown() path, it's safe since caller has already grabbed sb->s_umount semaphore. Reported-by: syzbot+1a8e2b31f2ac9bd3d148@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-f2fs-devel/0000000000005c7ccb061e032b9b@google.com Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") Signed-off-by: Chao Yu <chao@kernel.org> --- fs/f2fs/file.c | 3 +++ 1 file changed, 3 insertions(+)