From: Chao Yu <chao@xxxxxxxxxx> [ Upstream commit 458c15dfbce62c35fefd9ca637b20a051309c9f1 ] syzbot reports a bug as below: general protection fault, probably for non-canonical address 0xdffffc0000000009: 0000 [#1] PREEMPT SMP KASAN RIP: 0010:__lock_acquire+0x69/0x2000 kernel/locking/lockdep.c:4942 Call Trace: lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5691 __raw_write_lock include/linux/rwlock_api_smp.h:209 [inline] _raw_write_lock+0x2e/0x40 kernel/locking/spinlock.c:300 __drop_extent_tree+0x3ac/0x660 fs/f2fs/extent_cache.c:1100 f2fs_drop_extent_tree+0x17/0x30 fs/f2fs/extent_cache.c:1116 f2fs_insert_range+0x2d5/0x3c0 fs/f2fs/file.c:1664 f2fs_fallocate+0x4e4/0x6d0 fs/f2fs/file.c:1838 vfs_fallocate+0x54b/0x6b0 fs/open.c:324 ksys_fallocate fs/open.c:347 [inline] __do_sys_fallocate fs/open.c:355 [inline] __se_sys_fallocate fs/open.c:353 [inline] __x64_sys_fallocate+0xbd/0x100 fs/open.c:353 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd The root cause is race condition as below: - since it tries to remount rw filesystem, so that do_remount won't call sb_prepare_remount_readonly to block fallocate, there may be race condition in between remount and fallocate. - in f2fs_remount(), default_options() will reset mount option to default one, and then update it based on result of parse_options(), so there is a hole which race condition can happen. Thread A Thread B - f2fs_fill_super - parse_options - clear_opt(READ_EXTENT_CACHE) - f2fs_remount - default_options - set_opt(READ_EXTENT_CACHE) - f2fs_fallocate - f2fs_insert_range - f2fs_drop_extent_tree - __drop_extent_tree - __may_extent_tree - test_opt(READ_EXTENT_CACHE) return true - write_lock(&et->lock) access NULL pointer - parse_options - clear_opt(READ_EXTENT_CACHE) Cc: <stable@xxxxxxxxxxxxxxx> Reported-by: syzbot+d015b6c2fbb5c383bf08@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lore.kernel.org/linux-f2fs-devel/20230522124203.3838360-1-chao@xxxxxxxxxx Signed-off-by: Chao Yu <chao@xxxxxxxxxx> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/f2fs/super.c | 30 ++++++++++++++++++------------ 1 file changed, 18 insertions(+), 12 deletions(-) diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 36bb1c969e8bb..ff47aad636e5b 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -2040,9 +2040,22 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root) return 0; } -static void default_options(struct f2fs_sb_info *sbi) +static void default_options(struct f2fs_sb_info *sbi, bool remount) { /* init some FS parameters */ + if (!remount) { + set_opt(sbi, READ_EXTENT_CACHE); + clear_opt(sbi, DISABLE_CHECKPOINT); + + if (f2fs_hw_support_discard(sbi) || f2fs_hw_should_discard(sbi)) + set_opt(sbi, DISCARD); + + if (f2fs_sb_has_blkzoned(sbi)) + F2FS_OPTION(sbi).discard_unit = DISCARD_UNIT_SECTION; + else + F2FS_OPTION(sbi).discard_unit = DISCARD_UNIT_BLOCK; + } + if (f2fs_sb_has_readonly(sbi)) F2FS_OPTION(sbi).active_logs = NR_CURSEG_RO_TYPE; else @@ -2065,23 +2078,16 @@ static void default_options(struct f2fs_sb_info *sbi) set_opt(sbi, INLINE_XATTR); set_opt(sbi, INLINE_DATA); set_opt(sbi, INLINE_DENTRY); - set_opt(sbi, READ_EXTENT_CACHE); set_opt(sbi, NOHEAP); - clear_opt(sbi, DISABLE_CHECKPOINT); set_opt(sbi, MERGE_CHECKPOINT); F2FS_OPTION(sbi).unusable_cap = 0; sbi->sb->s_flags |= SB_LAZYTIME; if (!f2fs_sb_has_readonly(sbi) && !f2fs_readonly(sbi->sb)) set_opt(sbi, FLUSH_MERGE); - if (f2fs_hw_support_discard(sbi) || f2fs_hw_should_discard(sbi)) - set_opt(sbi, DISCARD); - if (f2fs_sb_has_blkzoned(sbi)) { + if (f2fs_sb_has_blkzoned(sbi)) F2FS_OPTION(sbi).fs_mode = FS_MODE_LFS; - F2FS_OPTION(sbi).discard_unit = DISCARD_UNIT_SECTION; - } else { + else F2FS_OPTION(sbi).fs_mode = FS_MODE_ADAPTIVE; - F2FS_OPTION(sbi).discard_unit = DISCARD_UNIT_BLOCK; - } #ifdef CONFIG_F2FS_FS_XATTR set_opt(sbi, XATTR_USER); @@ -2253,7 +2259,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data) clear_sbi_flag(sbi, SBI_NEED_SB_WRITE); } - default_options(sbi); + default_options(sbi, true); /* parse mount options */ err = parse_options(sb, data, true); @@ -4150,7 +4156,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent) sbi->s_chksum_seed = f2fs_chksum(sbi, ~0, raw_super->uuid, sizeof(raw_super->uuid)); - default_options(sbi); + default_options(sbi, false); /* parse mount options */ options = kstrdup((const char *)data, GFP_KERNEL); if (data && !options) { -- 2.40.1
