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 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary 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-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Mon Apr 9 13:58:16 CEST 2018 From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> [ 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@xxxxxxxxxx> Cc: linux-metag@xxxxxxxxxxxxxxx Ref: ac919f0883e5 ("metag: Traps") Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -6,4 +6,11 @@ #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 @@ -735,7 +735,7 @@ 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@xxxxxxxxxxxx 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