LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Eric W. Biederman" <ebiederm@xmission.com>
To: Linux-Arch <linux-arch@vger.kernel.org>
Cc: "Anton Ivanov" <anton.ivanov@kot-begemot.co.uk>,
	"Richard Weinberger" <richard.weinberger@gmail.com>,
	"Richard Weinberger" <richard@nod.at>,
	"Jeff Dike" <jdike@addtoit.com>,
	linux-um@lists.infradead.org, linux-kernel@vger.kernel.org,
	user-mode-linux-devel@lists.sourceforge.net,
	"Martin Pärtel" <martin.partel@gmail.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>
Subject: [REVIEW][PATCH 5/5] signal/um: More carefully relay signals in relay_signal.
Date: Sat, 28 Apr 2018 09:07:02 -0500	[thread overview]
Message-ID: <20180428140702.3925-5-ebiederm@xmission.com> (raw)
In-Reply-To: <87zi1nctut.fsf_-_@xmission.com>

There is a bug in relay signal.  It assumes that when a signal is
relayed the signal never uses a signal independent si_code, such
as SI_USER, SI_KERNEL, SI_QUEUE, ... SI_SIGIO etc.  In practice
siginfo was assuming it was relaying a signal with the SIL_FAULT
layout.  As that is the common cases for the signals it supported
that is a reasonable assumption.

Further user mode linux must be very careful when relaying different
kinds of signals to prevent an information leak.  This means simply
increasing the kinds of signals that are handled in relay_signal
is non-trivial.

Therefore use siginfo_layout and force_sig_fault to simplify
the signal relaying in relay_signal.

By taking advantage of the fact that user mode linux only works
on x86 and x86_64 we can assume that si_trapno can be ignored,
and that si_errno is always zero.

For the signals SIGLL, SIGFPE, SIGSEGV, SIGBUS, and SIGTRAP the only
fault handler I know of that sets si_errno is SIGTRAP TRAP_HWBKPT on a
few oddball architectures.  Those architectures have been modified to
use force_sig_ptrace_errno_trap.

Similarly only a few architectures set __ARCH_SI_TRAPNO.

At the point uml supports those architectures again these additional
cases can be examined and supported if desired in relay_signal.

Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@kot-begemot.co.uk>
Cc: Martin Pärtel <martin.partel@gmail.com>
Cc: user-mode-linux-devel@lists.sourceforge.net
Cc: linux-um@lists.infradead.org
Fixes: d3c1cfcdb43e ("um: pass siginfo to guest process")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 arch/um/kernel/trap.c | 38 ++++++++++++++------------------------
 1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index d18be983814a..ec9a42c14c56 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -286,9 +286,7 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 
 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
 {
-	struct faultinfo *fi;
-	struct siginfo clean_si;
-
+	int code, err;
 	if (!UPT_IS_USER(regs)) {
 		if (sig == SIGBUS)
 			printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
@@ -298,29 +296,21 @@ void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
 
 	arch_examine_signal(sig, regs);
 
-	clear_siginfo(&clean_si);
-	clean_si.si_signo = si->si_signo;
-	clean_si.si_errno = si->si_errno;
-	clean_si.si_code = si->si_code;
-	switch (sig) {
-	case SIGILL:
-	case SIGFPE:
-	case SIGSEGV:
-	case SIGBUS:
-	case SIGTRAP:
-		fi = UPT_FAULTINFO(regs);
-		clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
+	/* Is the signal layout for the signal known?
+	 * Signal data must be scrubbed to prevent information leaks.
+	 */
+	code = si->si_code;
+	err = si->si_errno;
+	if ((err == 0) && (siginfo_layout(sig, code) == SIL_FAULT)) {
+		struct faultinfo *fi = UPT_FAULTINFO(regs);
 		current->thread.arch.faultinfo = *fi;
-#ifdef __ARCH_SI_TRAPNO
-		clean_si.si_trapno = si->si_trapno;
-#endif
-		break;
-	default:
-		printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
-			sig, si->si_code);
+		force_sig_fault(sig, code, (void __user *)FAULT_ADDRESS(*fi),
+				current);
+	} else {
+		printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n",
+		       sig, code, err);
+		force_sig(sig, current);
 	}
-
-	force_sig_info(sig, &clean_si, current);
 }
 
 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
-- 
2.14.1

  parent reply	other threads:[~2018-04-28 14:07 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-20  1:01 [REVIEW][PATCH 00/17] siginfo bugfixes and cleanups Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 01/17] signal/alpha: Document a conflict with SI_USER for SIGFPE Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 02/17] sparc: fix compat siginfo ABI regression Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 03/17] signal/sh: Use force_sig_fault in hw_breakpoint_handler Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 04/17] signal/nds32: Use force_sig in unhandled_interruption and unhandled_exceptions Eric W. Biederman
2018-04-25 12:14   ` Vincent Chen
2018-04-20  1:03 ` [REVIEW][PATCH 05/17] signal/nds32: Use force_sig(SIGILL) in do_revisn Eric W. Biederman
2018-04-25 12:10   ` Vincent Chen
2018-04-25 16:13     ` [PATCH] signal/nds32: More information in do_revinsn Eric W. Biederman
2018-04-26  3:02       ` Vincent Chen
2018-04-20  1:03 ` [REVIEW][PATCH 06/17] signal: Ensure every siginfo we send has all bits initialized Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 07/17] signal: Reduce copy_siginfo_to_user to just copy_to_user Eric W. Biederman
2018-04-20  1:03 ` [REVIEW][PATCH 08/17] signal: Stop special casing TRAP_FIXME and FPE_FIXME in siginfo_layout Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 09/17] signal: Remove SEGV_BNDERR ifdefs Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 10/17] signal: Remove ifdefs for BUS_MCEERR_AR and BUS_MCEERR_AO Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 11/17] signal/alpha: Replace FPE_FIXME with FPE_FLTUNK Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 12/17] signal/ia64: " Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 13/17] signal/powerpc: " Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 14/17] signal/unicore32: Use FPE_FLTUNK instead of 0 in ucf64_raise_sigfpe Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 15/17] signal: Add TRAP_UNK si_code for undiagnosted trap exceptions Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 16/17] signal/alpha: Replace TRAP_FIXME with TRAP_UNK Eric W. Biederman
2018-04-20  1:04 ` [REVIEW][PATCH 17/17] signal/powerpc: " Eric W. Biederman
2018-04-20 14:35 ` [REVIEW][PATCH 00/22] Simplifying siginfo users Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 01/22] signal/alpha: Use send_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 02/22] signal/alpha: Use force_sig_fault " Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 03/22] signal/c6x: " Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 04/22] signal/hexagon: Use force_sig_fault as appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 05/22] signal/m68k: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 06/22] signal/microblaze: Remove the commented out force_sig_info in do_page_fault Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 07/22] signal/microblaze: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 08/22] signal/mips: " Eric W. Biederman
2018-05-09 15:14     ` Matt Redfearn
2018-05-10  2:39       ` Eric W. Biederman
2018-05-10  7:59         ` Matt Redfearn
2018-05-11  2:31           ` Eric W. Biederman
2018-04-20 14:37   ` [REVIEW][PATCH 09/22] signal/nds32: " Eric W. Biederman
2018-04-25 11:29     ` Vincent Chen
2018-04-25 15:57       ` Eric W. Biederman
2018-04-26  1:24         ` Greentime Hu
2018-04-20 14:37   ` [REVIEW][PATCH 10/22] signal/nios2: " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 11/22] signal/openrisc: " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 12/22] signal/parisc: Use force_sig_mceerr " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 13/22] signal/parisc: Use force_sig_fault " Eric W. Biederman
2018-04-21 17:24     ` Helge Deller
2018-04-20 14:38   ` [REVIEW][PATCH 14/22] signal/riscv: " Eric W. Biederman
2018-04-21  7:25     ` Christoph Hellwig
2018-04-24 15:31       ` [REVIEW][PATCH 23/22] signal/riscv: Replace do_trap_siginfo with force_sig_fault Eric W. Biederman
2018-04-23 19:11     ` [REVIEW][PATCH 14/22] signal/riscv: Use force_sig_fault where appropriate Palmer Dabbelt
2018-04-24 15:28       ` Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 15/22] signal/s390: " Eric W. Biederman
2018-04-23  5:44     ` Martin Schwidefsky
2018-04-20 14:38   ` [REVIEW][PATCH 16/22] signal/sh: " Eric W. Biederman
2018-04-20 14:55     ` Rich Felker
2018-05-28  9:19       ` Geert Uytterhoeven
2018-05-29 15:00         ` [PATCH] signal/sh: Stop gcc warning about an impossible case in do_divide_error Eric W. Biederman
2018-05-30  7:54           ` Sergei Shtylyov
2018-04-20 14:38   ` [REVIEW][PATCH 17/22] signal/sparc: Use send_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 18/22] signal/sparc: Use force_sig_fault " Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 19/22] signal/um: Use force_sig_fault in relay_signal Eric W. Biederman
2018-04-20 16:06     ` [uml-devel] " Anton Ivanov
2018-04-24  8:32       ` Richard Weinberger
2018-04-24  8:44         ` Anton Ivanov
2018-04-24 15:59           ` Eric W. Biederman
     [not found]             ` <CAMD8JhwgcWCp6c=O4-spNW1VdY5M-eAjr7M5PieeAfeTSe_4yw@mail.gmail.com>
2018-04-24 22:03               ` Martin Pärtel
2018-04-24 22:24                 ` Eric W. Biederman
2018-04-25 23:05                   ` Martin Pärtel
2018-04-28 14:02                     ` [REVIEW][PATCH 0/5] Improving siginfo_layout and fixing uml's relay_signal Eric W. Biederman
2018-04-28 14:06                       ` [REVIEW][PATCH 1/5] signal/signalfd: Remove __put_user from signalfd_copyinfo Eric W. Biederman
2018-04-28 14:06                       ` [REVIEW][PATCH 2/5] signal/signalfd: Add support for SIGSYS Eric W. Biederman
2018-04-28 14:07                       ` [REVIEW][PATCH 3/5] signal: Remove unncessary #ifdef SEGV_PKUERR in 32bit compat code Eric W. Biederman
2018-04-28 14:07                       ` [REVIEW][PATCH 4/5] signal: Extend siginfo_layout with SIL_FAULT_{MCEERR|BNDERR|PKUERR} Eric W. Biederman
2018-04-28 14:07                       ` Eric W. Biederman [this message]
2018-04-20 14:38   ` [REVIEW][PATCH 20/22] signal/um: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 14:38   ` [REVIEW][PATCH 21/22] signal/xtensa: Consistenly use SIGBUS in do_unaligned_user Eric W. Biederman
2018-04-20 16:06     ` Max Filippov
2018-04-20 14:38   ` [REVIEW][PATCH 22/22] signal/xtensa: Use force_sig_fault where appropriate Eric W. Biederman
2018-04-20 16:27     ` Max Filippov

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180428140702.3925-5-ebiederm@xmission.com \
    --to=ebiederm@xmission.com \
    --cc=anton.ivanov@kot-begemot.co.uk \
    --cc=jdike@addtoit.com \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-um@lists.infradead.org \
    --cc=martin.partel@gmail.com \
    --cc=richard.weinberger@gmail.com \
    --cc=richard@nod.at \
    --cc=user-mode-linux-devel@lists.sourceforge.net \
    --subject='Re: [REVIEW][PATCH 5/5] signal/um: More carefully relay signals in relay_signal.' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).