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Date: Fri, 18 Aug 2023 19:05:20 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net,
syzbot+e5600587fa9cbf8e3826@...kaller.appspotmail.com
Subject: Re: [f2fs-dev] [PATCH] f2fs: avoid false alarm of circular locking
On Fri, Aug 18, 2023 at 05:30:12PM -0700, Jaegeuk Kim wrote:
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.5.0-rc5-syzkaller-00353-gae545c3283dc #0 Not tainted
> ------------------------------------------------------
> syz-executor273/5027 is trying to acquire lock:
> ffff888077fe1fb0 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
> ffff888077fe1fb0 (&fi->i_sem){+.+.}-{3:3}, at: f2fs_add_inline_entry+0x300/0x6f0 fs/f2fs/inline.c:644
>
> but task is already holding lock:
> ffff888077fe07c8 (&fi->i_xattr_sem){.+.+}-{3:3}, at: f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
> ffff888077fe07c8 (&fi->i_xattr_sem){.+.+}-{3:3}, at: f2fs_add_dentry+0x92/0x230 fs/f2fs/dir.c:783
>
> which lock already depends on the new lock.
>
> the existing dependency chain (in reverse order) is:
>
> -> #1 (&fi->i_xattr_sem){.+.+}-{3:3}:
> down_read+0x9c/0x470 kernel/locking/rwsem.c:1520
> f2fs_down_read fs/f2fs/f2fs.h:2108 [inline]
> f2fs_getxattr+0xb1e/0x12c0 fs/f2fs/xattr.c:532
> __f2fs_get_acl+0x5a/0x900 fs/f2fs/acl.c:179
> f2fs_acl_create fs/f2fs/acl.c:377 [inline]
> f2fs_init_acl+0x15c/0xb30 fs/f2fs/acl.c:420
> f2fs_init_inode_metadata+0x159/0x1290 fs/f2fs/dir.c:558
> f2fs_add_regular_entry+0x79e/0xb90 fs/f2fs/dir.c:740
> f2fs_add_dentry+0x1de/0x230 fs/f2fs/dir.c:788
> f2fs_do_add_link+0x190/0x280 fs/f2fs/dir.c:827
> f2fs_add_link fs/f2fs/f2fs.h:3554 [inline]
> f2fs_mkdir+0x377/0x620 fs/f2fs/namei.c:781
> vfs_mkdir+0x532/0x7e0 fs/namei.c:4117
> do_mkdirat+0x2a9/0x330 fs/namei.c:4140
> __do_sys_mkdir fs/namei.c:4160 [inline]
> __se_sys_mkdir fs/namei.c:4158 [inline]
> __x64_sys_mkdir+0xf2/0x140 fs/namei.c:4158
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> -> #0 (&fi->i_sem){+.+.}-{3:3}:
> check_prev_add kernel/locking/lockdep.c:3142 [inline]
> check_prevs_add kernel/locking/lockdep.c:3261 [inline]
> validate_chain kernel/locking/lockdep.c:3876 [inline]
> __lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5144
> lock_acquire kernel/locking/lockdep.c:5761 [inline]
> lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5726
> down_write+0x93/0x200 kernel/locking/rwsem.c:1573
> f2fs_down_write fs/f2fs/f2fs.h:2133 [inline]
> f2fs_add_inline_entry+0x300/0x6f0 fs/f2fs/inline.c:644
> f2fs_add_dentry+0xa6/0x230 fs/f2fs/dir.c:784
> f2fs_do_add_link+0x190/0x280 fs/f2fs/dir.c:827
> f2fs_add_link fs/f2fs/f2fs.h:3554 [inline]
> f2fs_mkdir+0x377/0x620 fs/f2fs/namei.c:781
> vfs_mkdir+0x532/0x7e0 fs/namei.c:4117
> ovl_do_mkdir fs/overlayfs/overlayfs.h:196 [inline]
> ovl_mkdir_real+0xb5/0x370 fs/overlayfs/dir.c:146
> ovl_workdir_create+0x3de/0x820 fs/overlayfs/super.c:309
> ovl_make_workdir fs/overlayfs/super.c:711 [inline]
> ovl_get_workdir fs/overlayfs/super.c:864 [inline]
> ovl_fill_super+0xdab/0x6180 fs/overlayfs/super.c:1400
> vfs_get_super+0xf9/0x290 fs/super.c:1152
> vfs_get_tree+0x88/0x350 fs/super.c:1519
> do_new_mount fs/namespace.c:3335 [inline]
> path_mount+0x1492/0x1ed0 fs/namespace.c:3662
> do_mount fs/namespace.c:3675 [inline]
> __do_sys_mount fs/namespace.c:3884 [inline]
> __se_sys_mount fs/namespace.c:3861 [inline]
> __x64_sys_mount+0x293/0x310 fs/namespace.c:3861
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> other info that might help us debug this:
>
> Possible unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> rlock(&fi->i_xattr_sem);
> lock(&fi->i_sem);
> lock(&fi->i_xattr_sem);
> lock(&fi->i_sem);
>
> Reported-and-tested-by: syzbot+e5600587fa9cbf8e3826@...kaller.appspotmail.com
> Fixes: 5eda1ad1aaff "f2fs: fix deadlock in i_xattr_sem and inode page lock"
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Tested-by: Guenter Roeck <linux@...ck-us.net>
> ---
> fs/f2fs/f2fs.h | 24 +++++++++++++++---------
> fs/f2fs/inline.c | 3 ++-
> 2 files changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index c602ff2403b6..c0b7417f1d87 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2122,15 +2122,6 @@ static inline int f2fs_down_read_trylock(struct f2fs_rwsem *sem)
> return down_read_trylock(&sem->internal_rwsem);
> }
>
> -#ifdef CONFIG_DEBUG_LOCK_ALLOC
> -static inline void f2fs_down_read_nested(struct f2fs_rwsem *sem, int subclass)
> -{
> - down_read_nested(&sem->internal_rwsem, subclass);
> -}
> -#else
> -#define f2fs_down_read_nested(sem, subclass) f2fs_down_read(sem)
> -#endif
> -
> static inline void f2fs_up_read(struct f2fs_rwsem *sem)
> {
> up_read(&sem->internal_rwsem);
> @@ -2141,6 +2132,21 @@ static inline void f2fs_down_write(struct f2fs_rwsem *sem)
> down_write(&sem->internal_rwsem);
> }
>
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> +static inline void f2fs_down_read_nested(struct f2fs_rwsem *sem, int subclass)
> +{
> + down_read_nested(&sem->internal_rwsem, subclass);
> +}
> +
> +static inline void f2fs_down_write_nested(struct f2fs_rwsem *sem, int subclass)
> +{
> + down_write_nested(&sem->internal_rwsem, subclass);
> +}
> +#else
> +#define f2fs_down_read_nested(sem, subclass) f2fs_down_read(sem)
> +#define f2fs_down_write_nested(sem, subclass) f2fs_down_write(sem)
> +#endif
> +
> static inline int f2fs_down_write_trylock(struct f2fs_rwsem *sem)
> {
> return down_write_trylock(&sem->internal_rwsem);
> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> index 4638fee16a91..0d185ad5e469 100644
> --- a/fs/f2fs/inline.c
> +++ b/fs/f2fs/inline.c
> @@ -641,7 +641,8 @@ int f2fs_add_inline_entry(struct inode *dir, const struct f2fs_filename *fname,
> }
>
> if (inode) {
> - f2fs_down_write(&F2FS_I(inode)->i_sem);
> + f2fs_down_write_nested(&F2FS_I(inode)->i_sem,
> + SINGLE_DEPTH_NESTING);
> page = f2fs_init_inode_metadata(inode, dir, fname, ipage);
> if (IS_ERR(page)) {
> err = PTR_ERR(page);
> --
> 2.42.0.rc1.204.g551eb34607-goog
>
>
>
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> Linux-f2fs-devel@...ts.sourceforge.net
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