[PATCH v3 10/10] ext4: Check for overflow when allocating tables

[Simon Glass]

An overflow could cause too little memory to be allocated, thus
potentially causing undefined behaviour. Add a check for overflow.

Since blk_bmaps and inode_bmaps use the same size, share the variable.

Signed-off-by: Simon Glass <s...@chromium.org>
---

(no changes since v2)

Changes in v2:
- Use Linux macros instead of gcc built-ins

 fs/ext4/ext4_write.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c
index a48d1fd26be..a9a53214dce 100644
--- a/fs/ext4/ext4_write.c
+++ b/fs/ext4/ext4_write.c
@@ -607,6 +607,7 @@ int ext4fs_init(void)
        int i;
        uint32_t real_free_blocks = 0;
        struct ext_filesystem *fs = get_fs();
+       size_t alloc_size;
 
        /* check for a reasonable block size, no more than 64K */
        if (LOG2_BLOCK_SIZE(ext4fs_root) > 16)
@@ -643,7 +644,9 @@ int ext4fs_init(void)
        }
 
        /* load all the available bitmap block of the partition */
-       fs->blk_bmaps = zalloc(fs->no_blkgrp * sizeof(char *));
+       if (check_mul_overflow(fs->no_blkgrp, sizeof(char *), &alloc_size))
+               goto fail;
+       fs->blk_bmaps = zalloc(alloc_size);
        if (!fs->blk_bmaps)
                goto fail;
        for (i = 0; i < fs->no_blkgrp; i++) {
@@ -663,7 +666,7 @@ int ext4fs_init(void)
        }
 
        /* load all the available inode bitmap of the partition */
-       fs->inode_bmaps = zalloc(fs->no_blkgrp * sizeof(unsigned char *));
+       fs->inode_bmaps = zalloc(alloc_size);
        if (!fs->inode_bmaps)
                goto fail;
        for (i = 0; i < fs->no_blkgrp; i++) {
-- 
2.43.0