Re: [PATCH net V3 2/2] ptr_ring: fail on large queue size (>64K)
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2018-02-08 04:52:40
On Thu, Feb 08, 2018 at 11:59:25AM +0800, Jason Wang wrote:
quoted hunk ↗ jump to hunk
We need limit the maximum size of queue, otherwise it may cause several side effects e.g slab will warn when the size exceeds KMALLOC_MAX_SIZE. Using KMALLOC_MAX_SIZE still looks too so this patch tries to limit it to 64K. This value could be revisited if we found a real case that needs more. Reported-by: syzbot+e4d4f9ddd4295539735d@syzkaller.appspotmail.com Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers") Signed-off-by: Jason Wang <redacted> --- include/linux/ptr_ring.h | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h index 2af71a7..5858d48 100644 --- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h@@ -44,6 +44,8 @@ struct ptr_ring { void **queue; };
Seems like a weird location for a define. Either put defines on top of the file, or near where they are used. I prefer the second option.
+#define PTR_RING_MAX_ALLOC 65536 +
I guess it's an arbitrary number. Seems like a sufficiently large one, but pls add a comment so readers don't wonder. And please explain what it does: /* Callers can create ptr_ring structures with userspace-supplied * parameters. This sets a limit on the size to make that usecase * safe. If you ever change this, make sure to audit all callers. */ Also I think we should generally use either hex 0x10000 or (1 << 16).
quoted hunk ↗ jump to hunk
/* Note: callers invoking this in a loop must use a compiler barrier, * for example cpu_relax(). *@@ -466,6 +468,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r, static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp) { + if (size > PTR_RING_MAX_ALLOC) + return NULL; return kvmalloc_array(size, sizeof(void *), gfp | __GFP_ZERO); }-- 2.7.4