From 02cc3e8037c5e85480dadb86e349b393500bd770 Mon Sep 17 00:00:00 2001 From: Ian Ray Date: Wed, 8 Nov 2017 15:35:10 +0000 Subject: [PATCH] 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 Signed-off-by: Martyn Welch Reviewed-by: Stefano Babic (cherry picked from commit ecdfb4195b20eb2dcde3c4083170016c13c69e8b) --- 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 31952f48b9..dac9545365 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 b0c7303aa4..9ee2caf2fa 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; }