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Date: Mon, 14 Sep 2020 10:26:31 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-fscrypt@...r.kernel.org,
Daniel Rosenberg <drosen@...gle.com>,
Jeff Layton <jlayton@...nel.org>,
linux-f2fs-devel@...ts.sourceforge.net,
linux-mtd@...ts.infradead.org, ceph-devel@...r.kernel.org,
linux-ext4@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH v2 04/11] f2fs: use
fscrypt_prepare_new_inode() and fscrypt_set_context()
On 09/13, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
>
> Convert f2fs to use the new functions fscrypt_prepare_new_inode() and
> fscrypt_set_context(). This avoids calling
> fscrypt_get_encryption_info() from under f2fs_lock_op(), which can
> deadlock because fscrypt_get_encryption_info() isn't GFP_NOFS-safe.
>
> For more details about this problem, see the earlier patch
> "fscrypt: add fscrypt_prepare_new_inode() and fscrypt_set_context()".
>
> This also fixes a f2fs-specific deadlock when the filesystem is mounted
> with '-o test_dummy_encryption' and a file is created in an unencrypted
> directory other than the root directory:
>
> INFO: task touch:207 blocked for more than 30 seconds.
> Not tainted 5.9.0-rc4-00099-g729e3d0919844 #2
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:touch state:D stack: 0 pid: 207 ppid: 167 flags:0x00000000
> Call Trace:
> [...]
> lock_page include/linux/pagemap.h:548 [inline]
> pagecache_get_page+0x25e/0x310 mm/filemap.c:1682
> find_or_create_page include/linux/pagemap.h:348 [inline]
> grab_cache_page include/linux/pagemap.h:424 [inline]
> f2fs_grab_cache_page fs/f2fs/f2fs.h:2395 [inline]
> f2fs_grab_cache_page fs/f2fs/f2fs.h:2373 [inline]
> __get_node_page.part.0+0x39/0x2d0 fs/f2fs/node.c:1350
> __get_node_page fs/f2fs/node.c:35 [inline]
> f2fs_get_node_page+0x2e/0x60 fs/f2fs/node.c:1399
> read_inline_xattr+0x88/0x140 fs/f2fs/xattr.c:288
> lookup_all_xattrs+0x1f9/0x2c0 fs/f2fs/xattr.c:344
> f2fs_getxattr+0x9b/0x160 fs/f2fs/xattr.c:532
> f2fs_get_context+0x1e/0x20 fs/f2fs/super.c:2460
> fscrypt_get_encryption_info+0x9b/0x450 fs/crypto/keysetup.c:472
> fscrypt_inherit_context+0x2f/0xb0 fs/crypto/policy.c:640
> f2fs_init_inode_metadata+0xab/0x340 fs/f2fs/dir.c:540
> f2fs_add_inline_entry+0x145/0x390 fs/f2fs/inline.c:621
> f2fs_add_dentry+0x31/0x80 fs/f2fs/dir.c:757
> f2fs_do_add_link+0xcd/0x130 fs/f2fs/dir.c:798
> f2fs_add_link fs/f2fs/f2fs.h:3234 [inline]
> f2fs_create+0x104/0x290 fs/f2fs/namei.c:344
> lookup_open.isra.0+0x2de/0x500 fs/namei.c:3103
> open_last_lookups+0xa9/0x340 fs/namei.c:3177
> path_openat+0x8f/0x1b0 fs/namei.c:3365
> do_filp_open+0x87/0x130 fs/namei.c:3395
> do_sys_openat2+0x96/0x150 fs/open.c:1168
> [...]
>
> That happened because f2fs_add_inline_entry() locks the directory
> inode's page in order to add the dentry, then f2fs_get_context() tries
> to lock it recursively in order to read the encryption xattr. This
> problem is specific to "test_dummy_encryption" because normally the
> directory's fscrypt_info would be set up prior to
> f2fs_add_inline_entry() in order to encrypt the new filename.
>
> Regardless, the new design fixes this test_dummy_encryption deadlock as
> well as potential deadlocks with fs reclaim, by setting up any needed
> fscrypt_info structs prior to taking so many locks.
>
> The test_dummy_encryption deadlock was reported by Daniel Rosenberg.
>
> Reported-by: Daniel Rosenberg <drosen@...gle.com>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Thanks.
Acked-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
> fs/f2fs/dir.c | 2 +-
> fs/f2fs/f2fs.h | 23 -----------------------
> fs/f2fs/namei.c | 7 ++++++-
> 3 files changed, 7 insertions(+), 25 deletions(-)
>
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index b2530b9507bd9..414bc94fbd546 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -537,7 +537,7 @@ struct page *f2fs_init_inode_metadata(struct inode *inode, struct inode *dir,
> goto put_error;
>
> if (IS_ENCRYPTED(inode)) {
> - err = fscrypt_inherit_context(dir, inode, page, false);
> + err = fscrypt_set_context(inode, page);
> if (err)
> goto put_error;
> }
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index d9e52a7f3702f..0503371f88ed4 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1315,13 +1315,6 @@ enum fsync_mode {
> #define IS_IO_TRACED_PAGE(page) (0)
> #endif
>
> -#ifdef CONFIG_FS_ENCRYPTION
> -#define DUMMY_ENCRYPTION_ENABLED(sbi) \
> - (unlikely(F2FS_OPTION(sbi).dummy_enc_ctx.ctx != NULL))
> -#else
> -#define DUMMY_ENCRYPTION_ENABLED(sbi) (0)
> -#endif
> -
> /* For compression */
> enum compress_algorithm_type {
> COMPRESS_LZO,
> @@ -4022,22 +4015,6 @@ static inline bool f2fs_lfs_mode(struct f2fs_sb_info *sbi)
> return F2FS_OPTION(sbi).fs_mode == FS_MODE_LFS;
> }
>
> -static inline bool f2fs_may_encrypt(struct inode *dir, struct inode *inode)
> -{
> -#ifdef CONFIG_FS_ENCRYPTION
> - struct f2fs_sb_info *sbi = F2FS_I_SB(dir);
> - umode_t mode = inode->i_mode;
> -
> - /*
> - * If the directory encrypted or dummy encryption enabled,
> - * then we should encrypt the inode.
> - */
> - if (IS_ENCRYPTED(dir) || DUMMY_ENCRYPTION_ENABLED(sbi))
> - return (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode));
> -#endif
> - return false;
> -}
> -
> static inline bool f2fs_may_compress(struct inode *inode)
> {
> if (IS_SWAPFILE(inode) || f2fs_is_pinned_file(inode) ||
> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> index 84e4bbc1a64de..45f324511a19e 100644
> --- a/fs/f2fs/namei.c
> +++ b/fs/f2fs/namei.c
> @@ -28,6 +28,7 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t mode)
> nid_t ino;
> struct inode *inode;
> bool nid_free = false;
> + bool encrypt = false;
> int xattr_size = 0;
> int err;
>
> @@ -69,13 +70,17 @@ static struct inode *f2fs_new_inode(struct inode *dir, umode_t mode)
> F2FS_I(inode)->i_projid = make_kprojid(&init_user_ns,
> F2FS_DEF_PROJID);
>
> + err = fscrypt_prepare_new_inode(dir, inode, &encrypt);
> + if (err)
> + goto fail_drop;
> +
> err = dquot_initialize(inode);
> if (err)
> goto fail_drop;
>
> set_inode_flag(inode, FI_NEW_INODE);
>
> - if (f2fs_may_encrypt(dir, inode))
> + if (encrypt)
> f2fs_set_encrypted_inode(inode);
>
> if (f2fs_sb_has_extra_attr(sbi)) {
> --
> 2.28.0
>
>
>
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@...ts.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
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