From: Eric Biggers ebiggers@google.com

Commit a80f7fcf1867 ("ext4: fixup ext4_fc_track_* functions' signature") extended the scope of the transaction in ext4_unlink() too far, making it include the call to ext4_find_entry(). However, ext4_find_entry() can deadlock when called from within a transaction because it may need to set up the directory's encryption key.

Fix this by restoring the transaction to its original scope.

Reported-by: syzbot+1a748d0007eeac3ab079@syzkaller.appspotmail.com Fixes: a80f7fcf1867 ("ext4: fixup ext4_fc_track_* functions' signature") Cc: stable@vger.kernel.org # v5.10+ Signed-off-by: Eric Biggers ebiggers@google.com --- fs/ext4/ext4.h | 4 ++-- fs/ext4/fast_commit.c | 2 +- fs/ext4/namei.c | 44 +++++++++++++++++++++++-------------------- 3 files changed, 27 insertions(+), 23 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 8d5453852f98e..acaa951ef1886 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -3619,8 +3619,8 @@ extern void ext4_initialize_dirent_tail(struct buffer_head *bh, unsigned int blocksize); extern int ext4_handle_dirty_dirblock(handle_t *handle, struct inode *inode, struct buffer_head *bh); -extern int __ext4_unlink(handle_t *handle, struct inode *dir, const struct qstr *d_name, - struct inode *inode); +extern int __ext4_unlink(struct inode *dir, const struct qstr *d_name, + struct inode *inode, struct dentry *dentry); extern int __ext4_link(struct inode *dir, struct inode *inode, struct dentry *dentry);

diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index 6d98f2b39b775..da0c8228cf9c3 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -1397,7 +1397,7 @@ static int ext4_fc_replay_unlink(struct super_block *sb, struct ext4_fc_tl *tl, return 0; }

- ret = __ext4_unlink(NULL, old_parent, &entry, inode); + ret = __ext4_unlink(old_parent, &entry, inode, NULL); /* -ENOENT ok coz it might not exist anymore. */ if (ret == -ENOENT) ret = 0; diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index c08c0aba18836..a789ea9b61a09 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -3204,14 +3204,20 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry) return retval; }

-int __ext4_unlink(handle_t *handle, struct inode *dir, const struct qstr *d_name, - struct inode *inode) +int __ext4_unlink(struct inode *dir, const struct qstr *d_name, + struct inode *inode, + struct dentry *dentry /* NULL during fast_commit recovery */) { int retval = -ENOENT; struct buffer_head *bh; struct ext4_dir_entry_2 *de; + handle_t *handle; int skip_remove_dentry = 0;

+ /* + * Keep this outside the transaction; it may have to set up the + * directory's encryption key, which isn't GFP_NOFS-safe. + */ bh = ext4_find_entry(dir, d_name, &de, NULL); if (IS_ERR(bh)) return PTR_ERR(bh); @@ -3228,7 +3234,14 @@ int __ext4_unlink(handle_t *handle, struct inode *dir, const struct qstr *d_name if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) skip_remove_dentry = 1; else - goto out; + goto out_bh; + } + + handle = ext4_journal_start(dir, EXT4_HT_DIR, + EXT4_DATA_TRANS_BLOCKS(dir->i_sb)); + if (IS_ERR(handle)) { + retval = PTR_ERR(handle); + goto out_bh; }

if (IS_DIRSYNC(dir)) @@ -3237,12 +3250,12 @@ int __ext4_unlink(handle_t *handle, struct inode *dir, const struct qstr *d_name if (!skip_remove_dentry) { retval = ext4_delete_entry(handle, dir, de, bh); if (retval) - goto out; + goto out_handle; dir->i_ctime = dir->i_mtime = current_time(dir); ext4_update_dx_flag(dir); retval = ext4_mark_inode_dirty(handle, dir); if (retval) - goto out; + goto out_handle; } else { retval = 0; } @@ -3255,15 +3268,17 @@ int __ext4_unlink(handle_t *handle, struct inode *dir, const struct qstr *d_name ext4_orphan_add(handle, inode); inode->i_ctime = current_time(inode); retval = ext4_mark_inode_dirty(handle, inode); - -out: + if (dentry && !retval) + ext4_fc_track_unlink(handle, dentry); +out_handle: + ext4_journal_stop(handle); +out_bh: brelse(bh); return retval; }

static int ext4_unlink(struct inode *dir, struct dentry *dentry) { - handle_t *handle; int retval;

if (unlikely(ext4_forced_shutdown(EXT4_SB(dir->i_sb)))) @@ -3281,16 +3296,7 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry) if (retval) goto out_trace;

- handle = ext4_journal_start(dir, EXT4_HT_DIR, - EXT4_DATA_TRANS_BLOCKS(dir->i_sb)); - if (IS_ERR(handle)) { - retval = PTR_ERR(handle); - goto out_trace; - } - - retval = __ext4_unlink(handle, dir, &dentry->d_name, d_inode(dentry)); - if (!retval) - ext4_fc_track_unlink(handle, dentry); + retval = __ext4_unlink(dir, &dentry->d_name, d_inode(dentry), dentry); #if IS_ENABLED(CONFIG_UNICODE) /* VFS negative dentries are incompatible with Encoding and * Case-insensitiveness. Eventually we'll want avoid @@ -3301,8 +3307,6 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry) if (IS_CASEFOLDED(dir)) d_invalidate(dentry); #endif - if (handle) - ext4_journal_stop(handle);

out_trace: trace_ext4_unlink_exit(dentry, retval);