[PATCH 4/6] lib/scatterlist: Do not leak pages when high-order allocation fails

Tvrtko Ursulin
2018-09-26T14:16:58Z

If a higher-order allocation fails, the existing abort and cleanup path
would consider all segments allocated so far as 0-order page allocations
and would therefore leak memory.

Fix this by cleaning up using sgl_free_n_order which allows the correct
page order to be passed in.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
---
lib/scatterlist.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 3cc01cd82242..0caed79d7291 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -481,7 +481,7 @@ struct scatterlist *sgl_alloc_order(unsigned long length, unsigned int order,
{
struct scatterlist *sgl, *sg;
struct page *page;
- unsigned int nent, nalloc;
+ unsigned int nent, nalloc, i;
u32 elem_len;

nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
@@ -501,17 +501,19 @@ struct scatterlist *sgl_alloc_order(unsigned long length, unsigned int order,

sg_init_table(sgl, nalloc);
sg = sgl;
+ i = 0;
while (length) {
elem_len = min_t(u64, length, PAGE_SIZE << order);
page = alloc_pages(gfp, order);
if (!page) {
- sgl_free(sgl);
+ sgl_free_n_order(sgl, i, order);
return NULL;
}

sg_set_page(sg, page, elem_len, 0);
length -= elem_len;
sg = sg_next(sg);
+ i++;
}
WARN_ONCE(length, "length = %ld\n", length);
if (nent_p)
--
2.17.1