ext3, ext4: avoid divide by zero
As it turns out, the kernel divides by EXT3_INODES_PER_GROUP(s) when
mounting an ext3 filesystem. If that number is zero, a crash follows.
Below a patch.
This crash was reported by Joeri de Ruiter, Carst Tankink and Pim Vullers.
Cc: <linux-ext4@vger.kernel.org>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8031dc0..1ca0f54 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1797,7 +1797,7 @@
sbi->s_desc_size = EXT4_MIN_DESC_SIZE;
sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
- if (EXT4_INODE_SIZE(sb) == 0)
+ if (EXT4_INODE_SIZE(sb) == 0 || EXT4_INODES_PER_GROUP(sb) == 0)
goto cantfind_ext4;
sbi->s_inodes_per_block = blocksize / EXT4_INODE_SIZE(sb);
if (sbi->s_inodes_per_block == 0)