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 4.4-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-powerpc-document-conflicts-with-si_user-and-sigfpe-and-sigtrap.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@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Apr 10 10:31:53 CEST 2018
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
[ 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@xxxxxxxxx>
Cc: Kumar Gala <kumar.gala@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
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@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -17,4 +17,19 @@
#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
@@ -771,7 +771,7 @@ 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);
}
@@ -793,7 +793,7 @@ bail:
void RunModeException(struct pt_regs *regs)
{
- _exception(SIGTRAP, regs, 0, 0);
+ _exception(SIGTRAP, regs, TRAP_FIXME, 0);
}
void __kprobes single_step_exception(struct pt_regs *regs)
@@ -828,7 +828,7 @@ 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))
@@ -1764,7 +1764,7 @@ 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);
@@ -1833,7 +1833,7 @@ 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@xxxxxxxxxxxx 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