On 10 April 2018 at 01:29, gregkh@linuxfoundation.org wrote:

This is a note to let you know that I've just added the patch titled

signal/arm: Document conflicts with SI_USER and SIGFPE

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: signal-arm-document-conflicts-with-si_user-and-sigfpe.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

Just like v4.4.y-rc, this patch broke ARM builds for 4.9.y-rc as well https://kernelci.org/build/stable-rc/branch/linux-4.9.y/kernel/v4.9.93-278-g...

Eric has already pointed out in earlier emails that this a noop so it can be dropped from all stable queues.

Regards, Amit Pundir

From foo@baz Mon Apr 9 17:09:24 CEST 2018 From: "Eric W. Biederman" ebiederm@xmission.com Date: Thu, 17 Aug 2017 17:07:46 -0500 Subject: signal/arm: Document conflicts with SI_USER and SIGFPE

From: "Eric W. Biederman" ebiederm@xmission.com

[ Upstream commit 7771c66457004977b616bab785209f49d164f527 ]

Setting si_code to 0 results in a userspace seeing an si_code of 0. This is the same si_code as SI_USER. Posix and common sense requires that SI_USER not be a signal specific si_code. As such this use of 0 for the si_code is a pretty horribly broken ABI.

Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a value of __SI_KILL and now sees a value of SIL_KILL with the result that uid and pid fields are copied and which might copying the si_addr field by accident but certainly not by design. Making this a very flakey implementation.

Utilizing FPE_FIXME, siginfo_layout will now return SIL_FAULT and the appropriate fields will be reliably copied.

Possible ABI fixes includee:

• Send the signal without siginfo
• Don't generate a signal
• Possibly assign and use an appropriate si_code
• Don't handle cases which can't happen

Cc: Russell King rmk@flint.arm.linux.org.uk Cc: linux-arm-kernel@lists.infradead.org Ref: 451436b7bbb2 ("[ARM] Add support code for ARM hardware vector floating point") History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

---

arch/arm/include/uapi/asm/siginfo.h | 13 +++++++++++++ arch/arm/vfp/vfpmodule.c | 2 +- 2 files changed, 14 insertions(+), 1 deletion(-) create mode 100644 arch/arm/include/uapi/asm/siginfo.h

--- /dev/null +++ b/arch/arm/include/uapi/asm/siginfo.h @@ -0,0 +1,13 @@ +#ifndef __ASM_SIGINFO_H +#define __ASM_SIGINFO_H

+#include <asm-generic/siginfo.h>

+/*

• • SIGFPE si_codes
• */

+#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */

+#endif --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -257,7 +257,7 @@ static void vfp_raise_exceptions(u32 exc

    if (exceptions == VFP_EXCEPTION_ERROR) {
            vfp_panic("unhandled bounce", inst);

•           vfp_raise_sigfpe(0, regs);
  

•           vfp_raise_sigfpe(FPE_FIXME, regs);
            return;
    }
  
  
  
  

Patches currently in stable-queue which might be from ebiederm@xmission.com are

queue-4.9/signal-metag-document-a-conflict-with-si_user-with-sigfpe.patch queue-4.9/pidns-disable-pid-allocation-if-pid_ns_prepare_proc-is-failed-in-alloc_pid.patch queue-4.9/signal-arm-document-conflicts-with-si_user-and-sigfpe.patch queue-4.9/signal-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.patch