From 31abdab9c11bb1694ecd1476a7edbe8e964d94ac Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 18 May 2013 02:38:52 -0400 Subject: [PATCH] hpfs: deadlock and race in directory lseek() For one thing, there's an ABBA deadlock on hpfs fs-wide lock and i_mutex in hpfs_dir_lseek() - there's a lot of methods that grab the former with the caller already holding the latter, so it must take i_mutex first. For another, locking the damn thing, carefully validating the offset, then dropping locks and assigning the offset is obviously racy. Moreover, we _must_ do hpfs_add_pos(), or the machinery in dnode.c won't modify the sucker on B-tree surgeries. Signed-off-by: Al Viro --- fs/hpfs/dir.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/fs/hpfs/dir.c b/fs/hpfs/dir.c index 546f6d39713a..834ac13c04b7 100644 --- a/fs/hpfs/dir.c +++ b/fs/hpfs/dir.c @@ -33,25 +33,27 @@ static loff_t hpfs_dir_lseek(struct file *filp, loff_t off, int whence) if (whence == SEEK_DATA || whence == SEEK_HOLE) return -EINVAL; + mutex_lock(&i->i_mutex); hpfs_lock(s); /*printk("dir lseek\n");*/ if (new_off == 0 || new_off == 1 || new_off == 11 || new_off == 12 || new_off == 13) goto ok; - mutex_lock(&i->i_mutex); pos = ((loff_t) hpfs_de_as_down_as_possible(s, hpfs_inode->i_dno) << 4) + 1; while (pos != new_off) { if (map_pos_dirent(i, &pos, &qbh)) hpfs_brelse4(&qbh); else goto fail; if (pos == 12) goto fail; } - mutex_unlock(&i->i_mutex); + hpfs_add_pos(i, &filp->f_pos); ok: + filp->f_pos = new_off; hpfs_unlock(s); - return filp->f_pos = new_off; -fail: mutex_unlock(&i->i_mutex); + return new_off; +fail: /*printk("illegal lseek: %016llx\n", new_off);*/ hpfs_unlock(s); + mutex_unlock(&i->i_mutex); return -ESPIPE; } -- 2.30.2