Re: [PATCH v5 1/4] sgl_alloc_order: remove 4 GiB limit, sgl_free() warning
From: Jason Gunthorpe <jgg@ziepe.ca>
Date: 2021-01-07 17:44:55
Also in:
linux-rdma, linux-scsi, lkml, target-devel
On Mon, Dec 28, 2020 at 06:49:52PM -0500, Douglas Gilbert wrote:
quoted hunk ↗ jump to hunk
diff --git a/lib/scatterlist.c b/lib/scatterlist.c index a59778946404..4986545beef9 100644 +++ b/lib/scatterlist.c@@ -554,13 +554,15 @@ EXPORT_SYMBOL(sg_alloc_table_from_pages); #ifdef CONFIG_SGL_ALLOC /** - * sgl_alloc_order - allocate a scatterlist and its pages + * sgl_alloc_order - allocate a scatterlist with equally sized elements * @length: Length in bytes of the scatterlist. Must be at least one - * @order: Second argument for alloc_pages() + * @order: Second argument for alloc_pages(). Each sgl element size will + * be (PAGE_SIZE*2^order) bytes * @chainable: Whether or not to allocate an extra element in the scatterlist - * for scatterlist chaining purposes + * for scatterlist chaining purposes * @gfp: Memory allocation flags - * @nent_p: [out] Number of entries in the scatterlist that have pages + * @nent_p: [out] Number of entries in the scatterlist that have pages. + * Ignored if NULL is given. * * Returns: A pointer to an initialized scatterlist or %NULL upon failure. */@@ -574,8 +576,8 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, u32 elem_len; nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); - /* Check for integer overflow */ - if (length > (nent << (PAGE_SHIFT + order))) + /* Integer overflow if: length > nent*2^(PAGE_SHIFT+order) */ + if (ilog2(length) > ilog2(nent) + PAGE_SHIFT + order) return NULL; nalloc = nent; if (chainable) {
This is a little bit too tortured now, how about this:
if (length >> (PAGE_SHIFT + order) >= UINT_MAX)
return NULL;
nent = length >> (PAGE_SHIFT + order);
if (length & ((1ULL << (PAGE_SHIFT + order)) - 1))
nent++;
if (chainable) {
if (check_add_overflow(nent, 1, &nalloc))
return NULL;
}
else
nalloc = nent;
Jason