From: Wojciech Lukowicz wlukowicz01@gmail.com
[ Upstream commit 48ba08374e779421ca34bd14b4834aae19fc3e6a ]
Using struct_size() to calculate the size of io_uring_buf_ring will sum the size of the struct and of the bufs array. However, the struct's fields are overlaid with the array making the calculated size larger than it should be.
When registering a ring with N * PAGE_SIZE / sizeof(struct io_uring_buf) entries, i.e. with fully filled pages, the calculated size will span one more page than it should and io_uring will try to pin the following page. Depending on how the application allocated the ring, it might succeed using an unrelated page or fail returning EFAULT.
The size of the ring should be the product of ring_entries and the size of io_uring_buf, i.e. the size of the bufs array only.
Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers") Signed-off-by: Wojciech Lukowicz wlukowicz01@gmail.com Reviewed-by: Gabriel Krisman Bertazi krisman@suse.de Link: https://lore.kernel.org/r/20230218184141.70891-1-wlukowicz01@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/kbuf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 4a6401080c1f8..3002dc8271959 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -505,7 +505,7 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg) }
pages = io_pin_pages(reg.ring_addr, - struct_size(br, bufs, reg.ring_entries), + flex_array_size(br, bufs, reg.ring_entries), &nr_pages); if (IS_ERR(pages)) { kfree(free_bl);