This is a note to let you know that I've just added the patch titled
signal/metag: Document a conflict with SI_USER with SIGFPE
to the 4.4-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-metag-document-a-conflict-with-si_user-with-sigfpe.patch and it can be found in the queue-4.4 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 Tue Apr 10 10:31:53 CEST 2018
From: "Eric W. Biederman" ebiederm@xmission.com Date: Tue, 1 Aug 2017 10:37:40 -0500 Subject: signal/metag: Document a conflict with SI_USER with SIGFPE
From: "Eric W. Biederman" ebiederm@xmission.com
[ Upstream commit b80328be53c215346b153769267b38f531d89b4f ]
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 hat 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.
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 Hogan james.hogan@imgtec.com Cc: linux-metag@vger.kernel.org Ref: ac919f0883e5 ("metag: Traps") 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/metag/include/uapi/asm/siginfo.h | 7 +++++++ arch/metag/kernel/traps.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-)
--- a/arch/metag/include/uapi/asm/siginfo.h +++ b/arch/metag/include/uapi/asm/siginfo.h @@ -5,4 +5,11 @@
#include <asm-generic/siginfo.h>
+/* + * SIGFPE si_codes + */ +#ifdef __KERNEL__ +#define FPE_FIXME 0 /* Broken dup of SI_USER */ +#endif /* __KERNEL__ */ + #endif --- a/arch/metag/kernel/traps.c +++ b/arch/metag/kernel/traps.c @@ -732,7 +732,7 @@ TBIRES fpe_handler(TBIRES State, int Sig else if (error_state & TXSTAT_FPE_INEXACT_BIT) info.si_code = FPE_FLTRES; else - info.si_code = 0; + info.si_code = FPE_FIXME; info.si_errno = 0; info.si_addr = (__force void __user *)regs->ctx.CurrPC; force_sig_info(SIGFPE, &info, current);
Patches currently in stable-queue which might be from ebiederm@xmission.com are
queue-4.4/signal-metag-document-a-conflict-with-si_user-with-sigfpe.patch queue-4.4/pidns-disable-pid-allocation-if-pid_ns_prepare_proc-is-failed-in-alloc_pid.patch queue-4.4/signal-arm-document-conflicts-with-si_user-and-sigfpe.patch queue-4.4/signal-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.patch