From be6f0d0bae229ebd03e9bfe736f78e2d6b35885f Mon Sep 17 00:00:00 2001 From: "T.J. Mercier" Date: Wed, 22 Jul 2026 13:54:42 -0700 Subject: [PATCH] selftests: drv-net: ncdevmem: Open /dev/udmabuf O_RDONLY Write permissions on the /dev/udmabuf device file are not required to issue ioctls and allocate udmabufs. Applications should be opening this file as O_RDONLY. The BPF dmabuf_iter selftest already does this. [1] Users are pointing to these selftests as examples of how use udmabuf, and encountering permission errors on systems where write permissions are not available on /dev/udmabuf. Apply the principle of least privilege to selftests which use udmabuf by removing the write access mode from drivers/net/hw/ncdevmem.c. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c?h=v7.1#n49 Signed-off-by: T.J. Mercier Reviewed-by: Bobby Eshleman Link: https://patch.msgid.link/20260722205442.1894665-1-tjmercier@google.com Signed-off-by: Jakub Kicinski --- tools/testing/selftests/drivers/net/hw/ncdevmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/drivers/net/hw/ncdevmem.c b/tools/testing/selftests/drivers/net/hw/ncdevmem.c index d96e8a3b5a65..ffe1d5c1fa4e 100644 --- a/tools/testing/selftests/drivers/net/hw/ncdevmem.c +++ b/tools/testing/selftests/drivers/net/hw/ncdevmem.c @@ -150,7 +150,7 @@ static struct memory_buffer *udmabuf_alloc(size_t size) ctx->size = size; - ctx->devfd = open("/dev/udmabuf", O_RDWR); + ctx->devfd = open("/dev/udmabuf", O_RDONLY); if (ctx->devfd < 0) { pr_err("[skip,no-udmabuf: Unable to access DMA buffer device file]"); goto err_free_ctx;