From 084be43b751df7133c94c6bf556bc61bd6297406 Mon Sep 17 00:00:00 2001 From: Paul Emge Date: Mon, 8 Jul 2019 16:37:06 -0700 Subject: [PATCH] ext4: gracefully fail on divide-by-0 This patch checks for 0 in several ext4 headers and gracefully fails instead of raising a divide-by-0 exception. Signed-off-by: Paul Emge --- fs/ext4/ext4_common.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c index 8a142e2e6a..5bf78b530a 100644 --- a/fs/ext4/ext4_common.c +++ b/fs/ext4/ext4_common.c @@ -1571,8 +1571,12 @@ static int ext4fs_blockgroup int log2blksz = get_fs()->dev_desc->log2blksz; int desc_size = get_fs()->gdsize; + if (desc_size == 0) + return 0; desc_per_blk = EXT2_BLOCK_SIZE(data) / desc_size; + if (desc_per_blk == 0) + return 0; blkno = le32_to_cpu(data->sblock.first_data_block) + 1 + group / desc_per_blk; blkoff = (group % desc_per_blk) * desc_size; @@ -1602,6 +1606,10 @@ int ext4fs_read_inode(struct ext2_data *data, int ino, struct ext2_inode *inode) /* It is easier to calculate if the first inode is 0. */ ino--; + if ( le32_to_cpu(sblock->inodes_per_group) == 0 || fs->inodesz == 0) { + free(blkgrp); + return 0; + } status = ext4fs_blockgroup(data, ino / le32_to_cpu (sblock->inodes_per_group), blkgrp); if (status == 0) { @@ -1610,6 +1618,10 @@ int ext4fs_read_inode(struct ext2_data *data, int ino, struct ext2_inode *inode) } inodes_per_block = EXT2_BLOCK_SIZE(data) / fs->inodesz; + if ( inodes_per_block == 0 ) { + free(blkgrp); + return 0; + } blkno = ext4fs_bg_get_inode_table_id(blkgrp, fs) + (ino % le32_to_cpu(sblock->inodes_per_group)) / inodes_per_block; blkoff = (ino % inodes_per_block) * fs->inodesz; -- 2.25.1