| Message ID | 20220113002001.3498383-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | staging: rtl8723bs: Check for NULL header value | expand |
On Wed, Jan 12, 2022 at 04:20:01PM -0800, Kees Cook wrote: > When building with -Warray-bounds, the following warning is emitted: > > In file included from ./include/linux/string.h:253, > from ./arch/x86/include/asm/page_32.h:22, > from ./arch/x86/include/asm/page.h:14, > from ./arch/x86/include/asm/thread_info.h:12, > from ./include/linux/thread_info.h:60, > from ./arch/x86/include/asm/preempt.h:7, > from ./include/linux/preempt.h:78, > from ./include/linux/rcupdate.h:27, > from ./include/linux/rculist.h:11, > from ./include/linux/sched/signal.h:5, > from ./drivers/staging/rtl8723bs/include/drv_types.h:17, > from drivers/staging/rtl8723bs/core/rtw_recv.c:7: > In function 'memcpy', > inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2: > ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds] > 41 | #define __underlying_memcpy __builtin_memcpy > | ^ > > This is because the compiler sees it is possible for "ptr" to be a NULL > value, It's not really possible though. I bet it's just saying that because of the NULL check in get_recvframe_data(). Meanwhile we already have dereferenced "precvframe" so GCC should know that the NULL check can never be true. > and concludes that it has zero size and attempts to copy to it > would overflow. Instead, detect the NULL return and error out early. > > Cc: Larry Finger <Larry.Finger@lwfinger.net> > Cc: Phillip Potter <phil@philpotter.co.uk> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Michael Straube <straube.linux@gmail.com> > Cc: Fabio Aiuto <fabioaiuto83@gmail.com> > Cc: linux-staging@lists.linux.dev > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > drivers/staging/rtl8723bs/core/rtw_recv.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c > index 41bfca549c64..61135c49322b 100644 > --- a/drivers/staging/rtl8723bs/core/rtw_recv.c > +++ b/drivers/staging/rtl8723bs/core/rtw_recv.c > @@ -1513,6 +1513,9 @@ static signed int wlanhdr_to_ethhdr(union recv_frame *precvframe) > u8 *ptr = get_recvframe_data(precvframe) ; /* point to frame_ctrl field */ > struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib; > > + if (!ptr) > + return _FAIL; > + Can we put a comment to say /* Silence GCC false positive with -Warray-bounds */ We should have a standard comment so that we can grep for this ten years from now an remove any outdated work arounds. regards, dan carpenter
On Wed, Jan 12, 2022 at 04:20:01PM -0800, Kees Cook wrote: > When building with -Warray-bounds, the following warning is emitted: > > In file included from ./include/linux/string.h:253, > from ./arch/x86/include/asm/page_32.h:22, > from ./arch/x86/include/asm/page.h:14, > from ./arch/x86/include/asm/thread_info.h:12, > from ./include/linux/thread_info.h:60, > from ./arch/x86/include/asm/preempt.h:7, > from ./include/linux/preempt.h:78, > from ./include/linux/rcupdate.h:27, > from ./include/linux/rculist.h:11, > from ./include/linux/sched/signal.h:5, > from ./drivers/staging/rtl8723bs/include/drv_types.h:17, > from drivers/staging/rtl8723bs/core/rtw_recv.c:7: > In function 'memcpy', > inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2: > ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds] > 41 | #define __underlying_memcpy __builtin_memcpy > | ^ > > This is because the compiler sees it is possible for "ptr" to be a NULL > value, and concludes that it has zero size and attempts to copy to it > would overflow. Instead, detect the NULL return and error out early. > > Cc: Larry Finger <Larry.Finger@lwfinger.net> > Cc: Phillip Potter <phil@philpotter.co.uk> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Michael Straube <straube.linux@gmail.com> > Cc: Fabio Aiuto <fabioaiuto83@gmail.com> > Cc: linux-staging@lists.linux.dev > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > drivers/staging/rtl8723bs/core/rtw_recv.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c > index 41bfca549c64..61135c49322b 100644 > --- a/drivers/staging/rtl8723bs/core/rtw_recv.c > +++ b/drivers/staging/rtl8723bs/core/rtw_recv.c > @@ -1513,6 +1513,9 @@ static signed int wlanhdr_to_ethhdr(union recv_frame *precvframe) > u8 *ptr = get_recvframe_data(precvframe) ; /* point to frame_ctrl field */ > struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib; > > + if (!ptr) > + return _FAIL; This will never happen, so let's not paper over compiler issues with stuff like this please. As the call to get_recvframe_data() is only done in one place in this driver (in all drivers that look like this as well), it can just be replaced with the real code instead of the nonsensical test for NULL and then the compiler should be happy. I'll gladly take that fix instead of this one, as that would be the correct solution here. thanks, greg k-h
On Thu, Jan 13, 2022 at 10:13:46AM +0100, Greg Kroah-Hartman wrote: > On Wed, Jan 12, 2022 at 04:20:01PM -0800, Kees Cook wrote: > > When building with -Warray-bounds, the following warning is emitted: > > > > In file included from ./include/linux/string.h:253, > > from ./arch/x86/include/asm/page_32.h:22, > > from ./arch/x86/include/asm/page.h:14, > > from ./arch/x86/include/asm/thread_info.h:12, > > from ./include/linux/thread_info.h:60, > > from ./arch/x86/include/asm/preempt.h:7, > > from ./include/linux/preempt.h:78, > > from ./include/linux/rcupdate.h:27, > > from ./include/linux/rculist.h:11, > > from ./include/linux/sched/signal.h:5, > > from ./drivers/staging/rtl8723bs/include/drv_types.h:17, > > from drivers/staging/rtl8723bs/core/rtw_recv.c:7: > > In function 'memcpy', > > inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2: > > ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds] > > 41 | #define __underlying_memcpy __builtin_memcpy > > | ^ > > > > This is because the compiler sees it is possible for "ptr" to be a NULL > > value, and concludes that it has zero size and attempts to copy to it > > would overflow. Instead, detect the NULL return and error out early. > > > > Cc: Larry Finger <Larry.Finger@lwfinger.net> > > Cc: Phillip Potter <phil@philpotter.co.uk> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > Cc: Michael Straube <straube.linux@gmail.com> > > Cc: Fabio Aiuto <fabioaiuto83@gmail.com> > > Cc: linux-staging@lists.linux.dev > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > drivers/staging/rtl8723bs/core/rtw_recv.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c > > index 41bfca549c64..61135c49322b 100644 > > --- a/drivers/staging/rtl8723bs/core/rtw_recv.c > > +++ b/drivers/staging/rtl8723bs/core/rtw_recv.c > > @@ -1513,6 +1513,9 @@ static signed int wlanhdr_to_ethhdr(union recv_frame *precvframe) > > u8 *ptr = get_recvframe_data(precvframe) ; /* point to frame_ctrl field */ > > struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib; > > > > + if (!ptr) > > + return _FAIL; > > This will never happen, so let's not paper over compiler issues with > stuff like this please. > > As the call to get_recvframe_data() is only done in one place in this > driver (in all drivers that look like this as well), it can just be > replaced with the real code instead of the nonsensical test for NULL and > then the compiler should be happy. > > I'll gladly take that fix instead of this one, as that would be the > correct solution here. I changed it around, but it doesn't help. I assume this is because we build with -fno-delete-null-pointer-checks, so the compiler continues to assume it's possible for the incoming argument to be NULL. Should I rearrange this to do a NULL check for precvframe before all the assignments in addition to removing get_recvframe_data()? -Kees
On Thu, Jan 13, 2022 at 10:29:04AM -0800, Kees Cook wrote: > On Thu, Jan 13, 2022 at 10:13:46AM +0100, Greg Kroah-Hartman wrote: > > On Wed, Jan 12, 2022 at 04:20:01PM -0800, Kees Cook wrote: > > > When building with -Warray-bounds, the following warning is emitted: > > > > > > In file included from ./include/linux/string.h:253, > > > from ./arch/x86/include/asm/page_32.h:22, > > > from ./arch/x86/include/asm/page.h:14, > > > from ./arch/x86/include/asm/thread_info.h:12, > > > from ./include/linux/thread_info.h:60, > > > from ./arch/x86/include/asm/preempt.h:7, > > > from ./include/linux/preempt.h:78, > > > from ./include/linux/rcupdate.h:27, > > > from ./include/linux/rculist.h:11, > > > from ./include/linux/sched/signal.h:5, > > > from ./drivers/staging/rtl8723bs/include/drv_types.h:17, > > > from drivers/staging/rtl8723bs/core/rtw_recv.c:7: > > > In function 'memcpy', > > > inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2: > > > ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds] > > > 41 | #define __underlying_memcpy __builtin_memcpy > > > | ^ > > > > > > This is because the compiler sees it is possible for "ptr" to be a NULL > > > value, and concludes that it has zero size and attempts to copy to it > > > would overflow. Instead, detect the NULL return and error out early. > > > > > > Cc: Larry Finger <Larry.Finger@lwfinger.net> > > > Cc: Phillip Potter <phil@philpotter.co.uk> > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > Cc: Michael Straube <straube.linux@gmail.com> > > > Cc: Fabio Aiuto <fabioaiuto83@gmail.com> > > > Cc: linux-staging@lists.linux.dev > > > Signed-off-by: Kees Cook <keescook@chromium.org> > > > --- > > > drivers/staging/rtl8723bs/core/rtw_recv.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c > > > index 41bfca549c64..61135c49322b 100644 > > > --- a/drivers/staging/rtl8723bs/core/rtw_recv.c > > > +++ b/drivers/staging/rtl8723bs/core/rtw_recv.c > > > @@ -1513,6 +1513,9 @@ static signed int wlanhdr_to_ethhdr(union recv_frame *precvframe) > > > u8 *ptr = get_recvframe_data(precvframe) ; /* point to frame_ctrl field */ > > > struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib; > > > > > > + if (!ptr) > > > + return _FAIL; > > > > This will never happen, so let's not paper over compiler issues with > > stuff like this please. > > > > As the call to get_recvframe_data() is only done in one place in this > > driver (in all drivers that look like this as well), it can just be > > replaced with the real code instead of the nonsensical test for NULL and > > then the compiler should be happy. > > > > I'll gladly take that fix instead of this one, as that would be the > > correct solution here. > > I changed it around, but it doesn't help. I assume this is because we > build with -fno-delete-null-pointer-checks, so the compiler continues > to assume it's possible for the incoming argument to be NULL. That's a broken compiler then. > Should I rearrange this to do a NULL check for precvframe before all the > assignments in addition to removing get_recvframe_data()? If you walk the call-chain back, you will see that precvframe can't ever be NULL here (which is why this code doesn't crash), so don't check for something that is impossible to ever hit please just because the compiler is broken. thanks, greg k-h
On Thu, Jan 13, 2022 at 07:51:24PM +0100, Greg Kroah-Hartman wrote: > On Thu, Jan 13, 2022 at 10:29:04AM -0800, Kees Cook wrote: > > On Thu, Jan 13, 2022 at 10:13:46AM +0100, Greg Kroah-Hartman wrote: > > > On Wed, Jan 12, 2022 at 04:20:01PM -0800, Kees Cook wrote: > > > > When building with -Warray-bounds, the following warning is emitted: > > > > > > > > In file included from ./include/linux/string.h:253, > > > > from ./arch/x86/include/asm/page_32.h:22, > > > > from ./arch/x86/include/asm/page.h:14, > > > > from ./arch/x86/include/asm/thread_info.h:12, > > > > from ./include/linux/thread_info.h:60, > > > > from ./arch/x86/include/asm/preempt.h:7, > > > > from ./include/linux/preempt.h:78, > > > > from ./include/linux/rcupdate.h:27, > > > > from ./include/linux/rculist.h:11, > > > > from ./include/linux/sched/signal.h:5, > > > > from ./drivers/staging/rtl8723bs/include/drv_types.h:17, > > > > from drivers/staging/rtl8723bs/core/rtw_recv.c:7: > > > > In function 'memcpy', > > > > inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2: > > > > ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds] > > > > 41 | #define __underlying_memcpy __builtin_memcpy > > > > | ^ > > > > > > > > This is because the compiler sees it is possible for "ptr" to be a NULL > > > > value, and concludes that it has zero size and attempts to copy to it > > > > would overflow. Instead, detect the NULL return and error out early. > > > > > > > > Cc: Larry Finger <Larry.Finger@lwfinger.net> > > > > Cc: Phillip Potter <phil@philpotter.co.uk> > > > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > > > Cc: Michael Straube <straube.linux@gmail.com> > > > > Cc: Fabio Aiuto <fabioaiuto83@gmail.com> > > > > Cc: linux-staging@lists.linux.dev > > > > Signed-off-by: Kees Cook <keescook@chromium.org> > > > > --- > > > > drivers/staging/rtl8723bs/core/rtw_recv.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c > > > > index 41bfca549c64..61135c49322b 100644 > > > > --- a/drivers/staging/rtl8723bs/core/rtw_recv.c > > > > +++ b/drivers/staging/rtl8723bs/core/rtw_recv.c > > > > @@ -1513,6 +1513,9 @@ static signed int wlanhdr_to_ethhdr(union recv_frame *precvframe) > > > > u8 *ptr = get_recvframe_data(precvframe) ; /* point to frame_ctrl field */ > > > > struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib; > > > > > > > > + if (!ptr) > > > > + return _FAIL; > > > > > > This will never happen, so let's not paper over compiler issues with > > > stuff like this please. > > > > > > As the call to get_recvframe_data() is only done in one place in this > > > driver (in all drivers that look like this as well), it can just be > > > replaced with the real code instead of the nonsensical test for NULL and > > > then the compiler should be happy. > > > > > > I'll gladly take that fix instead of this one, as that would be the > > > correct solution here. > > > > I changed it around, but it doesn't help. I assume this is because we > > build with -fno-delete-null-pointer-checks, so the compiler continues > > to assume it's possible for the incoming argument to be NULL. > > That's a broken compiler then. > > > Should I rearrange this to do a NULL check for precvframe before all the > > assignments in addition to removing get_recvframe_data()? > > If you walk the call-chain back, you will see that precvframe can't ever > be NULL here (which is why this code doesn't crash), so don't check for > something that is impossible to ever hit please just because the > compiler is broken. I agree that the _original_ precvframe is always non-NULL, but the pointer landing at memcpy() gets updated along the way. It seems the new problem is that recvframe_pull() may return NULL and nothing is checking for that. Adding this silences the warning: diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/r8188eu/core/rtw_recv.c index 49a02d6239d6..946e659ae97a 100644 --- a/drivers/staging/r8188eu/core/rtw_recv.c +++ b/drivers/staging/r8188eu/core/rtw_recv.c @@ -1223,10 +1223,14 @@ static int wlanhdr_to_ethhdr(struct recv_frame *precvframe) eth_type = 0x8712; /* append rx status for mp test packets */ ptr = recvframe_pull(precvframe, (rmv_len - sizeof(struct ethhdr) + 2) - 24); + if (!ptr) + return _FAIL; memcpy(ptr, get_rxmem(precvframe), 24); ptr += 24; } else { ptr = recvframe_pull(precvframe, (rmv_len - sizeof(struct ethhdr) + (bsnaphdr ? 2 : 0))); + if (!ptr) + return _FAIL; } memcpy(ptr, pattrib->dst, ETH_ALEN); > > thanks, > > greg k-h
diff --git a/drivers/staging/rtl8723bs/core/rtw_recv.c b/drivers/staging/rtl8723bs/core/rtw_recv.c index 41bfca549c64..61135c49322b 100644 --- a/drivers/staging/rtl8723bs/core/rtw_recv.c +++ b/drivers/staging/rtl8723bs/core/rtw_recv.c @@ -1513,6 +1513,9 @@ static signed int wlanhdr_to_ethhdr(union recv_frame *precvframe) u8 *ptr = get_recvframe_data(precvframe) ; /* point to frame_ctrl field */ struct rx_pkt_attrib *pattrib = &precvframe->u.hdr.attrib; + if (!ptr) + return _FAIL; + if (pattrib->encrypt) recvframe_pull_tail(precvframe, pattrib->icv_len);
When building with -Warray-bounds, the following warning is emitted: In file included from ./include/linux/string.h:253, from ./arch/x86/include/asm/page_32.h:22, from ./arch/x86/include/asm/page.h:14, from ./arch/x86/include/asm/thread_info.h:12, from ./include/linux/thread_info.h:60, from ./arch/x86/include/asm/preempt.h:7, from ./include/linux/preempt.h:78, from ./include/linux/rcupdate.h:27, from ./include/linux/rculist.h:11, from ./include/linux/sched/signal.h:5, from ./drivers/staging/rtl8723bs/include/drv_types.h:17, from drivers/staging/rtl8723bs/core/rtw_recv.c:7: In function 'memcpy', inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2: ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds] 41 | #define __underlying_memcpy __builtin_memcpy | ^ This is because the compiler sees it is possible for "ptr" to be a NULL value, and concludes that it has zero size and attempts to copy to it would overflow. Instead, detect the NULL return and error out early. Cc: Larry Finger <Larry.Finger@lwfinger.net> Cc: Phillip Potter <phil@philpotter.co.uk> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Michael Straube <straube.linux@gmail.com> Cc: Fabio Aiuto <fabioaiuto83@gmail.com> Cc: linux-staging@lists.linux.dev Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/staging/rtl8723bs/core/rtw_recv.c | 3 +++ 1 file changed, 3 insertions(+)