Commit cf803903 authored Oct 25, 2011 by Darrick J. Wong Committed by Theodore Ts'o Oct 25, 2011

ext4: prevent stack overrun in ext4_file_open



In ext4_file_open, the filesystem records the mountpoint of the first
file that is opened after mounting the filesystem.  It does this by
allocating a 64-byte stack buffer, calling d_path() to grab the mount
point through which this file was accessed, and then memcpy()ing 64
bytes into the superblock's s_last_mounted field, starting from the
return value of d_path(), which is stored as "cp".  However, if cp >
buf (which it frequently is since path components are prepended
starting at the end of buf) then we can end up copying stack data into
the superblock.

Writing stack variables into the superblock doesn't sound like a great
idea, so use strlcpy instead.  Andi Kleen suggested using strlcpy
instead of strncpy.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

parent a4e5d88b

fs/ext4/file.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -181,7 +181,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
		path.dentry = mnt->mnt_root;
		cp = d_path(&path, buf, sizeof(buf));
		if (!IS_ERR(cp)) {
		memcpy(sbi->s_es->s_last_mounted, cp,
		strlcpy(sbi->s_es->s_last_mounted, cp,
		sizeof(sbi->s_es->s_last_mounted));
		ext4_mark_super_dirty(sb);
		}

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