From 909a4cf1ffe4b875c87abf38239a9bfd25167e0c Mon Sep 17 00:00:00 2001 From: Andreas Dilger Date: Wed, 26 Oct 2011 03:22:31 -0400 Subject: [PATCH] ext4: avoid setting directory i_nlink to zero If a directory with more than EXT4_LINK_MAX subdirectories, the nlink count is set to 1. Subsequently, if any subdirectories are deleted, ext4_dec_count() decrements the i_nlink count, which may go to 0 temporarily before being incremented back to 1. While this is done under i_mutex, which prevents races for directory and inode operations that check i_nlink, the temporary i_nlink == 0 case is exposed to userspace via stat() and similar calls that do not hold i_mutex. Instead, change the code to not decrement i_nlink count for any directories that do not already have i_nlink larger than 2. Reported-by: Cliff White Reviewed-by: Johann Lombardi Signed-off-by: Andreas Dilger Signed-off-by: "Theodore Ts'o" --- fs/ext4/namei.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index a067835bbac1..4a550aa07614 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -1706,9 +1706,8 @@ static void ext4_inc_count(handle_t *handle, struct inode *inode) */ static void ext4_dec_count(handle_t *handle, struct inode *inode) { - drop_nlink(inode); - if (S_ISDIR(inode->i_mode) && inode->i_nlink == 0) - inc_nlink(inode); + if (!S_ISDIR(inode->i_mode) || inode->i_nlink > 2) + drop_nlink(inode); } -- 2.39.2