In the Linux kernel, the following vulnerability has been resolved: dmaengine: mmp_pdma: fix wrong sg length in mmp_pdma_prep_slave_sg() I

In the Linux kernel, the following vulnerability has been resolved:

dmaengine: mmp_pdma: fix wrong sg length in mmp_pdma_prep_slave_sg()

In mmp_pdma_prep_slave_sg(), for_each_sg() iterates the scatterlist
putting each entry into 'sg', but the entry length is read from 'sgl'
(the list head) instead of 'sg' (the current entry):

 1for_each_sg(sgl, sg, sg_len, i) {
 2    addr = sg_dma_address(sg);
 3    avail = sg_dma_len(sgl);   /* should be 'sg' */

Consequently 'avail' is always the length of the first entry. For
multi-sg lists this causes out-of-bounds reads when a later entry is
shorter than the first, and silent data loss when it is longer.
Single-sg or uniformly-sized lists happen to mask the issue.