Messages in this thread Patch in this message | | | From | Ming Lei <> | Subject | [PATCH 1/2] sysfs: fix race between readdir and lseek | Date | Wed, 20 Mar 2013 23:25:24 +0800 |
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While readdir() is running, lseek() may set filp->f_pos as zero, then may leave filp->private_data pointing to one sysfs_dirent object without holding its reference counter, so the sysfs_dirent object may be used after free in next readdir().
This patch holds inode->i_mutex to avoid the problem since the lock is always held in readdir path.
Reported-by: Dave Jones <davej@redhat.com> Tested-by: Sasha Levin <levinsasha928@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Ming Lei <ming.lei@canonical.com> --- fs/sysfs/dir.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 2fbdff6..c9e1660 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -1058,10 +1058,21 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) return 0; } +static loff_t sysfs_dir_llseek(struct file *file, loff_t offset, int whence) +{ + struct inode *inode = file_inode(file); + loff_t ret; + + mutex_lock(&inode->i_mutex); + ret = generic_file_llseek(file, offset, whence); + mutex_unlock(&inode->i_mutex); + + return ret; +} const struct file_operations sysfs_dir_operations = { .read = generic_read_dir, .readdir = sysfs_readdir, .release = sysfs_dir_release, - .llseek = generic_file_llseek, + .llseek = sysfs_dir_llseek, }; -- 1.7.9.5
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