From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: [PATCH] [v3] x86, pkeys: fix siginfo ABI breakage from new field Date: Mon, 29 Feb 2016 14:17:33 -0800 Message-ID: <20160229221733.DC2C56B7@viggo.jf.intel.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Dave Hansen , dave.hansen@linux.intel.com, sfr@canb.auug.org.au, akpm@linux-foundation.org, tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com, peterz@infradead.org, linux-next@vger.kernel.org, deller@gmx.de List-Id: linux-next.vger.kernel.org This responds to the feedback from Ingo that we should be using explicitly-sized types and fixes a typo in the patch description. -- From: Dave Hansen 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 '__u32'. The __u32 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. 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 Acked-by: Stehen Rothwell Cc: Andrew Morton Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Peter Zijlstra Cc: linux-next@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Helge Deller --- 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 2016-02-29 09:22:45.327228965 -0800 +++ b/include/uapi/asm-generic/siginfo.h 2016-02-29 09:22:45.333229241 -0800 @@ -98,7 +98,7 @@ typedef struct siginfo { void __user *_upper; } _addr_bnd; /* used when si_code=SEGV_PKUERR */ - u64 _pkey; + __u32 _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 2016-02-29 09:22:45.330229103 -0800 +++ b/arch/mips/include/uapi/asm/siginfo.h 2016-02-29 09:22:45.333229241 -0800 @@ -93,7 +93,7 @@ typedef struct siginfo { void __user *_upper; } _addr_bnd; /* used when si_code=SEGV_PKUERR */ - u64 _pkey; + __u32 _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 2016-02-29 09:22:45.331229149 -0800 +++ b/arch/ia64/include/uapi/asm/siginfo.h 2016-02-29 09:22:45.333229241 -0800 @@ -70,7 +70,7 @@ typedef struct siginfo { void __user *_upper; } _addr_bnd; /* used when si_code=SEGV_PKUERR */ - u64 _pkey; + __u32 _pkey; }; } _sigfault; _