From: "Eric W. Biederman" ebiederm@xmission.com
[ Upstream commit b5daf2b9d1c9a2b4f03ca93f75913ba2da3b3eaa ]
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- arch/parisc/include/uapi/asm/siginfo.h | 7 +++++++ arch/parisc/kernel/traps.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/parisc/include/uapi/asm/siginfo.h b/arch/parisc/include/uapi/asm/siginfo.h index 8fd10f85c50e..882a8775441f 100644 --- a/arch/parisc/include/uapi/asm/siginfo.h +++ b/arch/parisc/include/uapi/asm/siginfo.h @@ -7,4 +7,11 @@
#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 378df9207406..3172cb52f703 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -627,7 +627,7 @@ 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;