[U-Boot] [PATCH v5 2/8] ext4: recover from filesystem corruption when reading

Martyn Welch
2017-11-08T15:35:10Z

From: Ian Ray <ian.ray@ge.com>

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>
---
fs/ext4/ext4_common.c | 10 ++++++++++
fs/ext4/ext4fs.c | 10 +++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 31952f4..dac9545 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -660,6 +660,11 @@ static int search_dir(struct ext2_inode *parent_inode, char *dirname)

offset = 0;
do {
+ if (offset & 3) {
+ printf("Badly aligned ext2_dirent\n");
+ break;
+ }
+
dir = (struct ext2_dirent *)(block_buffer + offset);
direntname = (char*)(dir) + sizeof(struct ext2_dirent);

@@ -880,6 +885,11 @@ static int unlink_filename(char *filename, unsigned int blknr)

offset = 0;
do {
+ if (offset & 3) {
+ printf("Badly aligned ext2_dirent\n");
+ break;
+ }
+
previous_dir = dir;
dir = (struct ext2_dirent *)(block_buffer + offset);
direntname = (char *)(dir) + sizeof(struct ext2_dirent);
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 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
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 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
(blockend >> log2blksz);
}
} else {
+ int n;
if (previous_block_number != -1) {
/* spill */
status = ext4fs_devread(delayed_start,
@@ -137,7 +141,11 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
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;
}
--
2.1.4