>From 2e2fc0c40d604e88748bba8d440763249c55b391 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Fri, 1 Jul 2016 15:03:39 +0200 Subject: [PATCH] ext4: validate number of clusters in group I've found that sbi->s_es->s_reserved_gdt_blocks is not validated before being used, so e.g. a value of 25600 will overflow the buffer head and corrupt random kernel memory (I've observed 20+ different stack traces due to these bugs, many of them long after the code has finished). Cc: Darrick J. Wong Signed-off-by: Vegard Nossum --- fs/ext4/balloc.c | 12 +++++------- fs/ext4/ext4.h | 4 ++++ fs/ext4/super.c | 19 +++++++++++++++++++ 3 files changed, 28 insertions(+), 7 deletions(-) diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 3020fd7..5a5c679 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -22,8 +22,6 @@ #include -static unsigned ext4_num_base_meta_clusters(struct super_block *sb, - ext4_group_t block_group); /* * balloc.c contains the blocks allocation and deallocation routines */ @@ -155,8 +153,8 @@ static unsigned ext4_num_overhead_clusters(struct super_block *sb, return num_clusters; } -static unsigned int num_clusters_in_group(struct super_block *sb, - ext4_group_t block_group) +unsigned int ext4_num_clusters_in_group(struct super_block *sb, + ext4_group_t block_group) { unsigned int blocks; @@ -237,7 +235,7 @@ static int ext4_init_block_bitmap(struct super_block *sb, * the blocksize * 8 ( which is the size of bitmap ), set rest * of the block bitmap to 1 */ - ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group), + ext4_mark_bitmap_end(ext4_num_clusters_in_group(sb, block_group), sb->s_blocksize * 8, bh->b_data); ext4_block_bitmap_csum_set(sb, block_group, gdp, bh); ext4_group_desc_csum_set(sb, block_group, gdp); @@ -251,7 +249,7 @@ unsigned ext4_free_clusters_after_init(struct super_block *sb, ext4_group_t block_group, struct ext4_group_desc *gdp) { - return num_clusters_in_group(sb, block_group) - + return ext4_num_clusters_in_group(sb, block_group) - ext4_num_overhead_clusters(sb, block_group, gdp); } @@ -817,7 +815,7 @@ unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group) * This function returns the number of file system metadata clusters at * the beginning of a block group, including the reserved gdt blocks. */ -static unsigned ext4_num_base_meta_clusters(struct super_block *sb, +unsigned ext4_num_base_meta_clusters(struct super_block *sb, ext4_group_t block_group) { struct ext4_sb_info *sbi = EXT4_SB(sb); diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index b84aa1ca..c325c95 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -2270,6 +2270,10 @@ extern ext4_grpblk_t ext4_block_group_offset(struct super_block *sb, extern int ext4_bg_has_super(struct super_block *sb, ext4_group_t group); extern unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group); +extern unsigned ext4_num_base_meta_clusters(struct super_block *sb, + ext4_group_t block_group); +extern unsigned int ext4_num_clusters_in_group(struct super_block *sb, + ext4_group_t block_group); extern ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode, ext4_fsblk_t goal, unsigned int flags, diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 563555e..05ec0a7 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3641,6 +3641,25 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) goto failed_mount; } sbi->s_groups_count = blocks_count; + + for (i = 0; i < sbi->s_groups_count; ++i) { + int bit_max; + + bit_max = ext4_num_base_meta_clusters(sb, i); + if ((bit_max >> 3) >= sb->s_blocksize) { + ext4_msg(sb, KERN_WARNING, "meta cluster base for " + "group %u exceeds block size", i); + goto failed_mount; + } + + bit_max = ext4_num_clusters_in_group(sb, i); + if ((bit_max >> 3) >= sb->s_blocksize) { + ext4_msg(sb, KERN_WARNING, "clusters in " + "group %u exceeds block size", i); + goto failed_mount; + } + } + sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count, (EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb))); db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) / -- 1.9.1