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Groups > linux.kernel > #1344514
| From | "H. Peter Anvin" <hpa@zytor.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field |
| Date | 2016-02-26 18:50 +0100 |
| Message-ID | <r6uGC-6KV-23@gated-at.bofh.it> (permalink) |
| References | <r6uwV-6GL-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On February 26, 2016 9:34:27 AM PST, Dave Hansen <dave@sr71.net> wrote:
>
>From: Dave Hansen <dave.hansen@linux.intel.com>
>
>Stephen Rothwell reported:
>
> http://lkml.kernel.org/r/20160226164406.065a1ffc@canb.auug.org.au
>
>that the Memory Protection Keys patches from the tip tree broke
>a build-time check on an ARM build because they changed the ABI
>of siginfo.
>
>A u64 was used for the protection key field in siginfo. When the
>containing union was aligned, this u64 unioned nicely with the
>two 'void *'s in _addr_bnd. But, on 32-bit, if the union was
>unaligned, the u64 might grow the size of the union, breaking the
>ABI for subsequent fields.
>
>To fix this, we replace the u64 with an 'unsigned long'. The long
>is guaranteed to union well with the pointers from _addr_bnd. It
>is also plenty large enough to store the 16-bit pkey we have today
>on x86. This also has the advantage that it allows existing 64-bit
>userspace to keep working without modification.
>
>I also shouldn't have been using a u64 in a userspace API to begin
>with.
>
>Fixes: cd0ea35ff551 ("signals, pkeys: Notify userspace about protection
>key faults")
>Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
>Cc: Stephen Rothwell <sfr@canb.auug.org.au>
>Cc: Andrew Morton <akpm@linux-foundation.org>
>Cc: Thomas Gleixner <tglx@linutronix.de>
>Cc: Ingo Molnar <mingo@elte.hu>
>Cc: "H. Peter Anvin" <hpa@zytor.com>
>Cc: Peter Zijlstra <peterz@infradead.org>
>Cc: linux-next@vger.kernel.org
>Cc: linux-kernel@vger.kernel.org
>Cc: Helge Deller <deller@gmx.de>
>---
>
> b/arch/ia64/include/uapi/asm/siginfo.h | 2 +-
> b/arch/mips/include/uapi/asm/siginfo.h | 2 +-
> b/include/uapi/asm-generic/siginfo.h | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
>
>diff -puN include/uapi/asm-generic/siginfo.h~pkeys-101-fix-siginfo
>include/uapi/asm-generic/siginfo.h
>---
>a/include/uapi/asm-generic/siginfo.h~pkeys-101-fix-siginfo 2016-02-26
>08:50:47.760659292 -0800
>+++ b/include/uapi/asm-generic/siginfo.h 2016-02-26 08:52:08.591330838
>-0800
>@@ -98,7 +98,7 @@ typedef struct siginfo {
> void __user *_upper;
> } _addr_bnd;
> /* used when si_code=SEGV_PKUERR */
>- u64 _pkey;
>+ unsigned long _pkey;
> };
> } _sigfault;
>
>diff -puN arch/mips/include/uapi/asm/siginfo.h~pkeys-101-fix-siginfo
>arch/mips/include/uapi/asm/siginfo.h
>---
>a/arch/mips/include/uapi/asm/siginfo.h~pkeys-101-fix-siginfo 2016-02-26
>08:51:50.357502608 -0800
>+++ b/arch/mips/include/uapi/asm/siginfo.h 2016-02-26
>08:51:55.206722873 -0800
>@@ -93,7 +93,7 @@ typedef struct siginfo {
> void __user *_upper;
> } _addr_bnd;
> /* used when si_code=SEGV_PKUERR */
>- u64 _pkey;
>+ unsigned long _pkey;
> };
> } _sigfault;
>
>diff -puN arch/ia64/include/uapi/asm/siginfo.h~pkeys-101-fix-siginfo
>arch/ia64/include/uapi/asm/siginfo.h
>---
>a/arch/ia64/include/uapi/asm/siginfo.h~pkeys-101-fix-siginfo 2016-02-26
>08:51:50.413505152 -0800
>+++ b/arch/ia64/include/uapi/asm/siginfo.h 2016-02-26
>08:52:00.806977252 -0800
>@@ -70,7 +70,7 @@ typedef struct siginfo {
> void __user *_upper;
> } _addr_bnd;
> /* used when si_code=SEGV_PKUERR */
>- u64 _pkey;
>+ unsigned long _pkey;
> };
> } _sigfault;
>
>_
__u64 is okay, "unsigned long" is really messy in the presence of 32-on-64 bit ABIs...
--
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.
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[PATCH] x86, pkeys: fix siginfo ABI breakage from new field Dave Hansen <dave@sr71.net> - 2016-02-26 18:40 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field "H. Peter Anvin" <hpa@zytor.com> - 2016-02-26 18:50 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Stephen Rothwell <sfr@canb.auug.org.au> - 2016-02-26 23:20 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Ingo Molnar <mingo@kernel.org> - 2016-02-27 12:50 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Dave Hansen <dave@sr71.net> - 2016-02-27 20:20 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field "H. Peter Anvin" <hpa@zytor.com> - 2016-02-27 20:40 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Stephen Rothwell <sfr@canb.auug.org.au> - 2016-02-28 00:30 +0100
[PATCH v2] signals, pkeys: make si_pkey 32 bits Stephen Rothwell <sfr@canb.auug.org.au> - 2016-02-28 00:50 +0100
Re: [PATCH v2] signals, pkeys: make si_pkey 32 bits Ingo Molnar <mingo@kernel.org> - 2016-02-29 09:00 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Ingo Molnar <mingo@kernel.org> - 2016-02-29 09:10 +0100
Re: [PATCH] x86, pkeys: fix siginfo ABI breakage from new field Stephen Rothwell <sfr@canb.auug.org.au> - 2016-03-01 00:00 +0100
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