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/dma-buf/udmabuf.c and 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 <[email protected]> Reviewed-by: Bobby Eshleman <[email protected]> --- tools/testing/selftests/drivers/dma-buf/udmabuf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/drivers/dma-buf/udmabuf.c b/tools/testing/selftests/drivers/dma-buf/udmabuf.c index d78aec662586..ced0b95c876c 100644 --- a/tools/testing/selftests/drivers/dma-buf/udmabuf.c +++ b/tools/testing/selftests/drivers/dma-buf/udmabuf.c @@ -140,7 +140,7 @@ int main(int argc, char *argv[]) ksft_print_header(); ksft_set_plan(7); - devfd = open("/dev/udmabuf", O_RDWR); + devfd = open("/dev/udmabuf", O_RDONLY); if (devfd < 0) { ksft_print_msg( "%s: [skip,no-udmabuf: Unable to access DMA buffer device file]\n", base-commit: 20f01a5565ce79923b75a2ac8e8ef2a1d7adf517 -- 2.55.0.229.g6434b31f56-goog
