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sysfs: fix race between readdir and lseek 

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ming Lei 2013-03-20 23:25:24 +08:00 committed by Greg Kroah-Hartman
parent a937536b86
commit 991f76f837
1 changed files with 12 additions and 1 deletions
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13
fs/sysfs/dir.c
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@ -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,
};