This is a note to let you know that I've just added the patch titled

signal/powerpc: Document conflicts with SI_USER and SIGFPE and SIGTRAP

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: signal-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.patch and it can be found in the queue-4.14 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 13:58:16 CEST 2018

From: "Eric W. Biederman" ebiederm@xmission.com Date: Sat, 19 Aug 2017 15:26:01 -0500 Subject: signal/powerpc: Document conflicts with SI_USER and SIGFPE and SIGTRAP

From: "Eric W. Biederman" ebiederm@xmission.com

[ Upstream commit cf4674c46c66e45f238f8f7e81af2a444b970c0a ]

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 and TRAP_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: Paul Mackerras paulus@samba.org Cc: Kumar Gala kumar.gala@freescale.com Cc: Michael Ellerman mpe@ellerman.id.au Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: linuxppc-dev@lists.ozlabs.org Ref: 9bad068c24d7 ("[PATCH] ppc32: support for e500 and 85xx") Ref: 0ed70f6105ef ("PPC32: Provide proper siginfo information on various exceptions.") 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/powerpc/include/uapi/asm/siginfo.h | 15 +++++++++++++++ arch/powerpc/kernel/traps.c | 10 +++++----- 2 files changed, 20 insertions(+), 5 deletions(-)

--- a/arch/powerpc/include/uapi/asm/siginfo.h +++ b/arch/powerpc/include/uapi/asm/siginfo.h @@ -18,4 +18,19 @@ #undef NSIGTRAP #define NSIGTRAP 4

+/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + +/* + * SIGTRAP si_codes + */ +#ifdef __KERNEL__ +#define TRAP_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + + #endif /* _ASM_POWERPC_SIGINFO_H */ --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -720,7 +720,7 @@ void unknown_exception(struct pt_regs *r printk("Bad trap at PC: %lx, SR: %lx, vector=%lx\n", regs->nip, regs->msr, regs->trap);

- _exception(SIGTRAP, regs, 0, 0); + _exception(SIGTRAP, regs, TRAP_FIXME, 0);

exception_exit(prev_state); } @@ -742,7 +742,7 @@ bail:

void RunModeException(struct pt_regs *regs) { - _exception(SIGTRAP, regs, 0, 0); + _exception(SIGTRAP, regs, TRAP_FIXME, 0); }

void single_step_exception(struct pt_regs *regs) @@ -781,7 +781,7 @@ static void emulate_single_step(struct p

static inline int __parse_fpscr(unsigned long fpscr) { - int ret = 0; + int ret = FPE_FIXME;

/* Invalid operation */ if ((fpscr & FPSCR_VE) && (fpscr & FPSCR_VX)) @@ -1769,7 +1769,7 @@ void SPEFloatingPointException(struct pt extern int do_spe_mathemu(struct pt_regs *regs); unsigned long spefscr; int fpexc_mode; - int code = 0; + int code = FPE_FIXME; int err;

flush_spe_to_thread(current); @@ -1838,7 +1838,7 @@ void SPEFloatingPointRoundException(stru printk(KERN_ERR "unrecognized spe instruction " "in %s at %lx\n", current->comm, regs->nip); } else { - _exception(SIGFPE, regs, 0, regs->nip); + _exception(SIGFPE, regs, FPE_FIXME, regs->nip); return; } }

Patches currently in stable-queue which might be from ebiederm@xmission.com are

queue-4.14/signal-metag-document-a-conflict-with-si_user-with-sigfpe.patch queue-4.14/signal-arm-document-conflicts-with-si_user-and-sigfpe.patch queue-4.14/signal-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.patch