ext4: recover from filesystem corruption when reading
Some fixes when reading EXT files and directory entries were identified
after using e2fuzz to corrupt an EXT3 filesystem:
- Stop reading directory entries if the offset becomes badly aligned.
- Avoid overwriting memory by clamping the length used to zero the buffer
in ext4fs_read_file. Also sanity check blocksize.
Signed-off-by: Ian Ray <ian.ray@ge.com>
Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
Reviewed-by: Stefano Babic <sbabic@denx.de>
diff --git a/fs/ext4/ext4fs.c b/fs/ext4/ext4fs.c
index b0c7303..9ee2caf 100644
--- a/fs/ext4/ext4fs.c
+++ b/fs/ext4/ext4fs.c
@@ -64,6 +64,9 @@
char *delayed_buf = NULL;
short status;
+ if (blocksize <= 0)
+ return -1;
+
/* Adjust len so it we can't read past the end of the file. */
if (len + pos > filesize)
len = (filesize - pos);
@@ -127,6 +130,7 @@
(blockend >> log2blksz);
}
} else {
+ int n;
if (previous_block_number != -1) {
/* spill */
status = ext4fs_devread(delayed_start,
@@ -137,7 +141,11 @@
return -1;
previous_block_number = -1;
}
- memset(buf, 0, blocksize - skipfirst);
+ /* Zero no more than `len' bytes. */
+ n = blocksize - skipfirst;
+ if (n > len)
+ n = len;
+ memset(buf, 0, n);
}
buf += blocksize - skipfirst;
}