GCC gets confused about the return value of get_cpu_var() possibly being NULL, so explicitly test for it before calls to memcpy() and memset(). Avoids warnings like this:

arch/um/drivers/virt-pci.c: In function 'um_pci_send_cmd': include/linux/fortify-string.h:48:33: warning: argument 1 null where non-null expected [-Wnonnull] 48 | #define __underlying_memcpy __builtin_memcpy | ^ include/linux/fortify-string.h:438:9: note: in expansion of macro '__underlying_memcpy' 438 | __underlying_##op(p, q, __fortify_size); \ | ^~~~~~~~~~~~~ include/linux/fortify-string.h:483:26: note: in expansion of macro '__fortify_memcpy_chk' 483 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ | ^~~~~~~~~~~~~~~~~~~~ arch/um/drivers/virt-pci.c:100:9: note: in expansion of macro 'memcpy' 100 | memcpy(buf, cmd, cmd_size); | ^~~~~~

While at it, avoid literal "8" and use stored sizeof(buf->data) in memset() and um_pci_send_cmd().

Reported-by: kernel test robot lkp@intel.com Link: https://lore.kernel.org/lkml/202211271212.SUZSC9f9-lkp@intel.com Fixes: ba38961a069b ("um: Enable FORTIFY_SOURCE") Cc: Richard Weinberger richard@nod.at Cc: Anton Ivanov anton.ivanov@cambridgegreys.com Cc: Johannes Berg johannes@sipsolutions.net Cc: "Michael S. Tsirkin" mst@redhat.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: Xiu Jianfeng xiujianfeng@huawei.com Cc: Vincent Whitchurch vincent.whitchurch@axis.com Cc: linux-um@lists.infradead.org Cc: stable@vger.kernel.org Signed-off-by: Kees Cook keescook@chromium.org --- I can take this via the hardening tree, since that's where I introduced the warning. :) --- arch/um/drivers/virt-pci.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c index acb55b302b14..3ac220dafec4 100644 --- a/arch/um/drivers/virt-pci.c +++ b/arch/um/drivers/virt-pci.c @@ -97,7 +97,8 @@ static int um_pci_send_cmd(struct um_pci_device *dev, }

buf = get_cpu_var(um_pci_msg_bufs); - memcpy(buf, cmd, cmd_size); + if (buf) + memcpy(buf, cmd, cmd_size);

if (posted) { u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC); @@ -182,6 +183,7 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset, struct um_pci_message_buffer *buf; u8 *data; unsigned long ret = ULONG_MAX; + size_t bytes = sizeof(buf->data);

if (!dev) return ULONG_MAX; @@ -189,7 +191,8 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset, buf = get_cpu_var(um_pci_msg_bufs); data = buf->data;

- memset(buf->data, 0xff, sizeof(buf->data)); + if (buf) + memset(data, 0xff, bytes);

switch (size) { case 1: @@ -204,7 +207,7 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset, goto out; }

- if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, 8)) + if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, bytes)) goto out;

switch (size) {