| Message ID | 20231116191409.work.634-kees@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | dma-buf: Replace strlcpy() with strscpy() | expand |
On Thu, Nov 16, 2023 at 11:14 AM Kees Cook <keescook@chromium.org> wrote: > > strlcpy() reads the entire source buffer first. This read may exceed > the destination size limit. This is both inefficient and can lead > to linear read overflows if a source string is not NUL-terminated[1]. > Additionally, it returns the size of the source string, not the > resulting size of the destination string. In an effort to remove strlcpy() > completely[2], replace strlcpy() here with strscpy(). > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1] > Link: https://github.com/KSPP/linux/issues/89 [2] > Cc: Sumit Semwal <sumit.semwal@linaro.org> > Cc: "Christian König" <christian.koenig@amd.com> > Cc: Azeem Shaikh <azeemshaikh38@gmail.com> > Cc: linux-media@vger.kernel.org > Cc: dri-devel@lists.freedesktop.org > Cc: linaro-mm-sig@lists.linaro.org > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: T.J. Mercier <tjmercier@google.com> strscpy returns -E2BIG when it truncates / force null-terminates which would provide the wrong argument for dynamic_dname, but dma_buf_set_name{_user} makes sure we have a null-terminated string of the appropriate maximum size in dmabuf->name.
Am 17.11.23 um 19:50 schrieb T.J. Mercier: > On Thu, Nov 16, 2023 at 11:14 AM Kees Cook <keescook@chromium.org> wrote: >> strlcpy() reads the entire source buffer first. This read may exceed >> the destination size limit. This is both inefficient and can lead >> to linear read overflows if a source string is not NUL-terminated[1]. >> Additionally, it returns the size of the source string, not the >> resulting size of the destination string. In an effort to remove strlcpy() >> completely[2], replace strlcpy() here with strscpy(). >> >> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1] >> Link: https://github.com/KSPP/linux/issues/89 [2] >> Cc: Sumit Semwal <sumit.semwal@linaro.org> >> Cc: "Christian König" <christian.koenig@amd.com> >> Cc: Azeem Shaikh <azeemshaikh38@gmail.com> >> Cc: linux-media@vger.kernel.org >> Cc: dri-devel@lists.freedesktop.org >> Cc: linaro-mm-sig@lists.linaro.org >> Signed-off-by: Kees Cook <keescook@chromium.org> > Reviewed-by: T.J. Mercier <tjmercier@google.com> > > strscpy returns -E2BIG when it truncates / force null-terminates which > would provide the wrong argument for dynamic_dname, but > dma_buf_set_name{_user} makes sure we have a null-terminated string of > the appropriate maximum size in dmabuf->name. Thanks for that background check, I was about to note that this might not be a good idea. Linus pretty clearly stated that he doesn't want to see patches like that one here, see this article as well. https://lwn.net/Articles/659214/ I think the commit message gives enough reason to merge the patch, so I'm going to push it to drm-misc-next. But please make sure to triple check stuff like this before sending. Thanks, Christian.
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 21916bba77d5..8fe5aa67b167 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -46,12 +46,12 @@ static char *dmabuffs_dname(struct dentry *dentry, char *buffer, int buflen) { struct dma_buf *dmabuf; char name[DMA_BUF_NAME_LEN]; - size_t ret = 0; + ssize_t ret = 0; dmabuf = dentry->d_fsdata; spin_lock(&dmabuf->name_lock); if (dmabuf->name) - ret = strlcpy(name, dmabuf->name, DMA_BUF_NAME_LEN); + ret = strscpy(name, dmabuf->name, sizeof(name)); spin_unlock(&dmabuf->name_lock); return dynamic_dname(buffer, buflen, "/%s:%s",
strlcpy() reads the entire source buffer first. This read may exceed the destination size limit. This is both inefficient and can lead to linear read overflows if a source string is not NUL-terminated[1]. Additionally, it returns the size of the source string, not the resulting size of the destination string. In an effort to remove strlcpy() completely[2], replace strlcpy() here with strscpy(). Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1] Link: https://github.com/KSPP/linux/issues/89 [2] Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: "Christian König" <christian.koenig@amd.com> Cc: Azeem Shaikh <azeemshaikh38@gmail.com> Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/dma-buf/dma-buf.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)