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ext4: recover from filesystem corruption when reading

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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>
This commit is contained in:
Ian Ray 2017-11-08 15:35:10 +00:00 committed by Stefano Babic
parent 2feec4eafd
commit ecdfb4195b
2 changed files with 19 additions and 1 deletions
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10
fs/ext4/ext4_common.c
View File

@ -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);

10
fs/ext4/ext4fs.c
View File

@ -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;
}