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| author | Theodore Ts'o <tytso@mit.edu> | 2016-07-05 20:01:52 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-08-16 09:35:00 +0200 |
| commit | 9cfaab733a0143f19de96c97c1876d56800478a4 (patch) | |
| tree | 642028b15675083b92506038f6aba6ef87509612 | |
| parent | efc588bf340f52863f9faa30970928e829c1043a (diff) | |
| download | linux-stable-9cfaab733a0143f19de96c97c1876d56800478a4.tar.gz linux-stable-9cfaab733a0143f19de96c97c1876d56800478a4.tar.bz2 linux-stable-9cfaab733a0143f19de96c97c1876d56800478a4.zip | |
ext4: validate s_reserved_gdt_blocks on mount
commit 5b9554dc5bf008ae7f68a52e3d7e76c0920938a2 upstream.
If s_reserved_gdt_blocks is extremely large, it's possible for
ext4_init_block_bitmap(), which is called when ext4 sets up an
uninitialized block bitmap, to corrupt random kernel memory. Add the
same checks which e2fsck has --- it must never be larger than
blocksize / sizeof(__u32) --- and then add a backup check in
ext4_init_block_bitmap() in case the superblock gets modified after
the file system is mounted.
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/ext4/balloc.c | 3 | ||||
| -rw-r--r-- | fs/ext4/super.c | 7 |
2 files changed, 10 insertions, 0 deletions
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 3020fd70c392..1ea505434a6e 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -208,6 +208,9 @@ static int ext4_init_block_bitmap(struct super_block *sb, memset(bh->b_data, 0, sb->s_blocksize); bit_max = ext4_num_base_meta_clusters(sb, block_group); + if ((bit_max >> 3) >= bh->b_size) + return -EFSCORRUPTED; + for (bit = 0; bit < bit_max; bit++) ext4_set_bit(bit, bh->b_data); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 3822a5aedc61..d7defc65fad0 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3416,6 +3416,13 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) goto failed_mount; } + if (le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) > (blocksize / 4)) { + ext4_msg(sb, KERN_ERR, + "Number of reserved GDT blocks insanely large: %d", + le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks)); + goto failed_mount; + } + if (sbi->s_mount_opt & EXT4_MOUNT_DAX) { err = bdev_dax_supported(sb, blocksize); if (err) |