Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  fs/omfs: reject s_sys_blocksize smaller than OMFS_DIR_START  omfs_fill_super() rejects oversized s_sys_blocksize values (> PAGE_SIZE), but it does not reject values smaller than OMFS_DIR_START (0x1b8 = 440).  Later, omfs_make_empty() uses      sbi->s_sys_blocksize - OMFS_DIR_START  as the length argument to memset().  Since s_sys_blocksize is u32, a crafted filesystem image with s_sys_blocksize < OMFS_DIR_START causes an unsigned underflow there, wrapping to a value near 2^32.  That drives a ~4 GiB memset() from bh->b_data + OMFS_DIR_START and overwrites kernel memory far beyond the backing block buffer.  Add the corresponding lower-bound check alongside the existing upper-bound check in omfs_fill_super(), so that malformed images are rejected during superblock validation before any filesystem data is processed.