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| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-08-01 06:25:01 +0300 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2018-01-12 23:21:03 +0300 |
| commit | b5daf2b9d1c9a2b4f03ca93f75913ba2da3b3eaa (patch) | |
| tree | 458b81054e341f824befef521db5d27c3dfbcb8e | |
| parent | 500d58300571b6602341b041f97c082a461ef994 (diff) | |
| download | linux-b5daf2b9d1c9a2b4f03ca93f75913ba2da3b3eaa.tar.xz | |
signal/parisc: Document a conflict with SI_USER with SIGFPE
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 reliably be copied.
This bug is 13 years old and parsic machines are no longer being built
so I don't know if it possible or worth fixing it. But it is at least
worth documenting this so other architectures don't make the same
mistake.
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: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
Ref: 313c01d3e3fd ("[PATCH] PA-RISC update for 2.6.0")
Histroy Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
| -rw-r--r-- | arch/parisc/include/uapi/asm/siginfo.h | 7 | ||||
| -rw-r--r-- | arch/parisc/kernel/traps.c | 2 |
2 files changed, 8 insertions, 1 deletions
diff --git a/arch/parisc/include/uapi/asm/siginfo.h b/arch/parisc/include/uapi/asm/siginfo.h index 4a1062e05aaf..be40331f757d 100644 --- a/arch/parisc/include/uapi/asm/siginfo.h +++ b/arch/parisc/include/uapi/asm/siginfo.h @@ -8,4 +8,11 @@ #include <asm-generic/siginfo.h> +/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + #endif diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c index 8453724b8009..c919e6c0a687 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -629,7 +629,7 @@ void notrace handle_interruption(int code, struct pt_regs *regs) si.si_signo = SIGFPE; /* Set to zero, and let the userspace app figure it out from the insn pointed to by si_addr */ - si.si_code = 0; + si.si_code = FPE_FIXME; si.si_addr = (void __user *) regs->iaoq[0]; force_sig_info(SIGFPE, &si, current); return; |