Patch "signal/arm: Document conflicts with SI_USER and SIGFPE" has been added to the 4.15-stable tree

Patch "signal/arm: Document conflicts with SI_USER and SIGFPE" has been added to the 4.15-stable tree

[gregkh]

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 4.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     signal-arm-document-conflicts-with-si_user-and-sigfpe.patch
and it can be found in the queue-4.15 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.


>From foo@baz Mon Apr  9 10:16:32 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-4.15/signal-metag-document-a-conflict-with-si_user-with-sigfpe.patch
queue-4.15/signal-arm-document-conflicts-with-si_user-and-sigfpe.patch
queue-4.15/signal-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.patch

Re: Patch "signal/arm: Document conflicts with SI_USER and SIGFPE" has been added to the 4.15-stable tree

[Eric W. Biederman]

<gregkh@linuxfoundation.org> writes:

> 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 4.15-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
>
> The filename of the patch is:
>      signal-arm-document-conflicts-with-si_user-and-sigfpe.patch
> and it can be found in the queue-4.15 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.

The patch is a noop functionality wise so I don't see the point in
backporting it to stable.

Eric


> From foo@baz Mon Apr  9 10:16:32 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-4.15/signal-metag-document-a-conflict-with-si_user-with-sigfpe.patch
> queue-4.15/signal-arm-document-conflicts-with-si_user-and-sigfpe.patch
> queue-4.15/signal-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.patch