4.15-stable review patch. If anyone has any objections, please let me know.
------------------ From: Kees Cook <keesc...@chromium.org> commit b5b38200ebe54879a7264cb6f33821f61c586a7e upstream. Successes in probe_kernel_read() would mask failures in copy_to_user() during read_mem(). Reported-by: Brad Spengler <spen...@grsecurity.net> Fixes: 22ec1a2aea73 ("/dev/mem: Add bounce buffer for copy-out") Cc: sta...@vger.kernel.org Signed-off-by: Kees Cook <keesc...@chromium.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- drivers/char/mem.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -137,7 +137,7 @@ static ssize_t read_mem(struct file *fil while (count > 0) { unsigned long remaining; - int allowed; + int allowed, probe; sz = size_inside_page(p, count); @@ -160,9 +160,9 @@ static ssize_t read_mem(struct file *fil if (!ptr) goto failed; - err = probe_kernel_read(bounce, ptr, sz); + probe = probe_kernel_read(bounce, ptr, sz); unxlate_dev_mem_ptr(p, ptr); - if (err) + if (probe) goto failed; remaining = copy_to_user(buf, bounce, sz);