Commit 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") did not take in account that the usage of BITS_PER_LONG in __GENMASK() was changed to __BITS_PER_LONG for UAPI-safety in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"). BITS_PER_LONG can not be used in UAPI headers as it derives from the kernel configuration and not from the current compiler invocation. When building compat userspace code or a compat vDSO its value will be incorrect.
Switch back to __BITS_PER_LONG.
Fixes: 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de --- include/uapi/linux/bits.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bits.h b/include/uapi/linux/bits.h index 682b406e10679dc8baa188830ab0811e7e3e13e3..a04afef9efca42f062e142fcb33f5d267512b1e5 100644 --- a/include/uapi/linux/bits.h +++ b/include/uapi/linux/bits.h @@ -4,9 +4,9 @@ #ifndef _UAPI_LINUX_BITS_H #define _UAPI_LINUX_BITS_H
-#define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (BITS_PER_LONG - 1 - (h)))) +#define __GENMASK(h, l) (((~_UL(0)) << (l)) & (~_UL(0) >> (__BITS_PER_LONG - 1 - (h))))
-#define __GENMASK_ULL(h, l) (((~_ULL(0)) << (l)) & (~_ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h)))) +#define __GENMASK_ULL(h, l) (((~_ULL(0)) << (l)) & (~_ULL(0) >> (__BITS_PER_LONG_LONG - 1 - (h))))
#define __GENMASK_U128(h, l) \ ((_BIT128((h)) << 1) - (_BIT128(l)))
--- base-commit: e271ed52b344ac02d4581286961d0c40acc54c03 change-id: 20250606-uapi-genmask-e07667de69ec
Best regards,
On Fri, Jun 06, 2025 at 10:23:57AM +0200, Thomas Weißschuh wrote:
Commit 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") did not take in account that the usage of BITS_PER_LONG in __GENMASK() was changed to __BITS_PER_LONG for UAPI-safety in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"). BITS_PER_LONG can not be used in UAPI headers as it derives from the kernel configuration and not from the current compiler invocation. When building compat userspace code or a compat vDSO its value will be incorrect.
Switch back to __BITS_PER_LONG.
Fixes: 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de
Thanks Thomas. I applied it in bitmap-for-next. Is that issue critical enough for you to send a pull request in -rc2?
Thanks, Yury
On Fri, Jun 06, 2025 at 10:20:56AM -0400, Yury Norov wrote:
On Fri, Jun 06, 2025 at 10:23:57AM +0200, Thomas Weißschuh wrote:
Commit 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") did not take in account that the usage of BITS_PER_LONG in __GENMASK() was changed to __BITS_PER_LONG for UAPI-safety in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"). BITS_PER_LONG can not be used in UAPI headers as it derives from the kernel configuration and not from the current compiler invocation. When building compat userspace code or a compat vDSO its value will be incorrect.
Switch back to __BITS_PER_LONG.
Fixes: 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de
Thanks Thomas. I applied it in bitmap-for-next. Is that issue critical enough for you to send a pull request in -rc2?
I have some patches that depend on it. These will probably end up in linux-next soonish and would then break there.
So having it in -rc2 would be nice.
Thanks
On Fri, Jun 06, 2025 at 04:32:22PM +0200, Thomas Weißschuh wrote:
On Fri, Jun 06, 2025 at 10:20:56AM -0400, Yury Norov wrote:
On Fri, Jun 06, 2025 at 10:23:57AM +0200, Thomas Weißschuh wrote:
Commit 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") did not take in account that the usage of BITS_PER_LONG in __GENMASK() was changed to __BITS_PER_LONG for UAPI-safety in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"). BITS_PER_LONG can not be used in UAPI headers as it derives from the kernel configuration and not from the current compiler invocation. When building compat userspace code or a compat vDSO its value will be incorrect.
Switch back to __BITS_PER_LONG.
Fixes: 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de
Thanks Thomas. I applied it in bitmap-for-next. Is that issue critical enough for you to send a pull request in -rc2?
I have some patches that depend on it. These will probably end up in linux-next soonish and would then break there.
So having it in -rc2 would be nice.
Thanks
Hi Thomas,
Thanks for pointing out the problem, may I ask in what config would cause "BITS_PER_LONG" to work incorrectly ?
I would love to test the difference between them and see what I can get, thanks.
Best regards, I Hsin Cheng
Hi I Hsin Cheng,
On Mon, Jun 09, 2025 at 03:47:49PM +0800, I Hsin Cheng wrote:
On Fri, Jun 06, 2025 at 04:32:22PM +0200, Thomas Weißschuh wrote:
On Fri, Jun 06, 2025 at 10:20:56AM -0400, Yury Norov wrote:
On Fri, Jun 06, 2025 at 10:23:57AM +0200, Thomas Weißschuh wrote:
Commit 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") did not take in account that the usage of BITS_PER_LONG in __GENMASK() was changed to __BITS_PER_LONG for UAPI-safety in commit 3c7a8e190bc5 ("uapi: introduce uapi-friendly macros for GENMASK"). BITS_PER_LONG can not be used in UAPI headers as it derives from the kernel configuration and not from the current compiler invocation. When building compat userspace code or a compat vDSO its value will be incorrect.
Switch back to __BITS_PER_LONG.
Fixes: 1e7933a575ed ("uapi: Revert "bitops: avoid integer overflow in GENMASK(_ULL)"") Cc: stable@vger.kernel.org Signed-off-by: Thomas Weißschuh thomas.weissschuh@linutronix.de
Thanks Thomas. I applied it in bitmap-for-next. Is that issue critical enough for you to send a pull request in -rc2?
I have some patches that depend on it. These will probably end up in linux-next soonish and would then break there.
So having it in -rc2 would be nice.
Thanks for pointing out the problem, may I ask in what config would cause "BITS_PER_LONG" to work incorrectly ?
In my specific usecase it was when building the powerpc compat vDSO. For an easy reproducer use:
diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c index 93ef801a97ef..948619848a3b 100644 --- a/lib/vdso/gettimeofday.c +++ b/lib/vdso/gettimeofday.c @@ -16,6 +16,9 @@ # define VDSO_DELTA_MASK(vd) (vd->mask) #endif
+_Static_assert(__BITS_PER_LONG == sizeof(long) * 8); +_Static_assert(BITS_PER_LONG == sizeof(long) * 8); + #ifdef CONFIG_GENERIC_VDSO_OVERFLOW_PROTECT static __always_inline bool vdso_delta_ok(const struct vdso_clock *vc, u64 delta) {
I would love to test the difference between them and see what I can get, thanks.
Looking at this again, the UAPI headers don't even define BITS_PER_LONG. The vDSO just incorrectly ends up also using the regular kernel headers.
Thomas
linux-stable-mirror@lists.linaro.org
-
I Hsin Cheng -
Thomas Weißschuh -
Yury Norov