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authorTheodore Ts'o <tytso@mit.edu>2016-07-05 20:01:52 -0400
committerTheodore Ts'o <tytso@mit.edu>2016-07-05 20:01:52 -0400
commit5b9554dc5bf008ae7f68a52e3d7e76c0920938a2 (patch)
tree0e77ba0fce0b9b68920ae7f7d1561ffcb690ba04
parentde9e9181bc066d63d78b768e95b5d949e2a8673a (diff)
ext4: validate s_reserved_gdt_blocks on mount
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> Cc: stable@vger.kernel.org
-rw-r--r--fs/ext4/balloc.c3
-rw-r--r--fs/ext4/super.c7
2 files changed, 10 insertions, 0 deletions
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 0b8105b3293d..799a92bdf577 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 5664ee66b301..13c49af7a06a 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)