| Message ID | 1654008188-3183-1-git-send-email-chen45464546@163.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v3] mm: page_frag: Warn_on when frag_alloc size is bigger than PAGE_SIZE | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On 5/31/22 07:43, Chen Lin wrote: > netdev_alloc_frag->page_frag_alloc may cause memory corruption in > the following process: > > 1. A netdev_alloc_frag function call need alloc 200 Bytes to build a skb. > > 2. Insufficient memory to alloc PAGE_FRAG_CACHE_MAX_ORDER(32K) in > __page_frag_cache_refill to fill frag cache, then one page(eg:4K) > is allocated, now current frag cache is 4K, alloc is success, > nc->pagecnt_bias--. > > 3. Then this 200 bytes skb in step 1 is freed, page->_refcount--. > > 4. Another netdev_alloc_frag function call need alloc 5k, page->_refcount > is equal to nc->pagecnt_bias, reset page count bias and offset to > start of new frag. page_frag_alloc will return the 4K memory for a > 5K memory request. > > 5. The caller write on the extra 1k memory which is not actual allocated > will cause memory corruption. > > page_frag_alloc is for fragmented allocation. We should warn the caller > to avoid memory corruption. > > When fragsz is larger than one page, we report the failure and return. > I don't think it is a good idea to make efforts to support the > allocation of more than one page in this function because the total > frag cache size(PAGE_FRAG_CACHE_MAX_SIZE 32768) is relatively small. > When the request is larger than one page, the caller should switch to > use other kernel interfaces, such as kmalloc and alloc_Pages. > > This bug is mainly caused by the reuse of the previously allocated > frag cache memory by the following LARGER allocations. This bug existed > before page_frag_alloc was ported from __netdev_alloc_frag in > net/core/skbuff.c, so most Linux versions have this problem. > > Signed-off-by: Chen Lin <chen45464546@163.com> > --- > mm/page_alloc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index e008a3d..ffc42b5 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5574,6 +5574,15 @@ void *page_frag_alloc_align(struct page_frag_cache *nc, > struct page *page; > int offset; > > + /* > + * frag_alloc is not suitable for memory alloc which fragsz > + * is bigger than PAGE_SIZE, use kmalloc or alloc_pages instead. > + */ > + if (WARN_ONCE(fragz > PAGE_SIZE, > + "alloc fragsz(%d) > PAGE_SIZE(%ld) not supported, alloc fail\n", > + fragsz, PAGE_SIZE)) > + return NULL; > + > if (unlikely(!nc->va)) { > refill: > page = __page_frag_cache_refill(nc, gfp_mask); I do not think this patch is needed, nor correct. (panic_on_warn=1 will panic the box) Or provide a stack trace ? Please fix the caller (presumably a network driver ?), and provide an appropriate Fixes: tag. Thanks.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e008a3d..ffc42b5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5574,6 +5574,15 @@ void *page_frag_alloc_align(struct page_frag_cache *nc, struct page *page; int offset; + /* + * frag_alloc is not suitable for memory alloc which fragsz + * is bigger than PAGE_SIZE, use kmalloc or alloc_pages instead. + */ + if (WARN_ONCE(fragz > PAGE_SIZE, + "alloc fragsz(%d) > PAGE_SIZE(%ld) not supported, alloc fail\n", + fragsz, PAGE_SIZE)) + return NULL; + if (unlikely(!nc->va)) { refill: page = __page_frag_cache_refill(nc, gfp_mask);
netdev_alloc_frag->page_frag_alloc may cause memory corruption in the following process: 1. A netdev_alloc_frag function call need alloc 200 Bytes to build a skb. 2. Insufficient memory to alloc PAGE_FRAG_CACHE_MAX_ORDER(32K) in __page_frag_cache_refill to fill frag cache, then one page(eg:4K) is allocated, now current frag cache is 4K, alloc is success, nc->pagecnt_bias--. 3. Then this 200 bytes skb in step 1 is freed, page->_refcount--. 4. Another netdev_alloc_frag function call need alloc 5k, page->_refcount is equal to nc->pagecnt_bias, reset page count bias and offset to start of new frag. page_frag_alloc will return the 4K memory for a 5K memory request. 5. The caller write on the extra 1k memory which is not actual allocated will cause memory corruption. page_frag_alloc is for fragmented allocation. We should warn the caller to avoid memory corruption. When fragsz is larger than one page, we report the failure and return. I don't think it is a good idea to make efforts to support the allocation of more than one page in this function because the total frag cache size(PAGE_FRAG_CACHE_MAX_SIZE 32768) is relatively small. When the request is larger than one page, the caller should switch to use other kernel interfaces, such as kmalloc and alloc_Pages. This bug is mainly caused by the reuse of the previously allocated frag cache memory by the following LARGER allocations. This bug existed before page_frag_alloc was ported from __netdev_alloc_frag in net/core/skbuff.c, so most Linux versions have this problem. Signed-off-by: Chen Lin <chen45464546@163.com> --- mm/page_alloc.c | 9 +++++++++ 1 file changed, 9 insertions(+)