From: Maurizio Lombardi Date: Fri, 15 Jul 2022 12:50:13 +0000 (+0200) Subject: mm: prevent page_frag_alloc() from corrupting the memory X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=6ca31ef8cd708a5e823c40d69c1a2bda90cf037f;p=users%2Fjedix%2Flinux-maple.git mm: prevent page_frag_alloc() from corrupting the memory A number of drivers call page_frag_alloc() with a fragment's size > PAGE_SIZE. In low memory conditions, __page_frag_cache_refill() may fail the order 3 cache allocation and fall back to order 0; In this case, the cache will be smaller than the fragment, causing memory corruptions. Prevent this from happening by checking if the newly allocated cache is large enough for the fragment; if not, the allocation will fail and page_frag_alloc() will return NULL. Link: https://lkml.kernel.org/r/20220715125013.247085-1-mlombard@redhat.com Signed-off-by: Maurizio Lombardi Reviewed-by: Alexander Duyck Cc: Chen Lin Cc: Jakub Kicinski Signed-off-by: Andrew Morton --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 19a0e4a23b2f1..9d26c12f8e63a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5732,6 +5732,18 @@ refill: /* reset page count bias and offset to start of new frag */ nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; offset = size - fragsz; + if (unlikely(offset < 0)) { + /* + * The caller is trying to allocate a fragment + * with fragsz > PAGE_SIZE but the cache isn't big + * enough to satisfy the request, this may + * happen in low memory conditions. + * We don't release the cache page because + * it could make memory pressure worse + * so we simply return NULL here. + */ + return NULL; + } } nc->pagecnt_bias--;