linux-kernel - [PATCH 3.16 092/133] MIPS: Handle non word sized instructions when examining frame

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 22 Nov 2017 01:58:13 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Matt Redfearn" <matt.redfearn@...tec.com>,
        linux-mips@...ux-mips.org, "Ralf Baechle" <ralf@...ux-mips.org>,
        "Marcin Nowakowski" <marcin.nowakowski@...tec.com>,
        "James Hogan" <james.hogan@...tec.com>,
        "Paul Burton" <paul.burton@...tec.com>,
        "Ingo Molnar" <mingo@...nel.org>
Subject: [PATCH 3.16 092/133] MIPS: Handle non word sized instructions
 when examining frame

3.16.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Matt Redfearn <matt.redfearn@...tec.com>

commit 11887ed172a6960673f130dad8f8fb42778f64d7 upstream.

Commit 34c2f668d0f6b ("MIPS: microMIPS: Add unaligned access support.")
added fairly broken support for handling 16bit microMIPS instructions in
get_frame_info(). It adjusts the instruction pointer by 16bits in the
case of a 16bit sp move instruction, but not any other 16bit
instruction.

Commit b6c7a324df37 ("MIPS: Fix get_frame_info() handling of microMIPS
function size") goes some way to fixing get_frame_info() to iterate over
microMIPS instuctions, but the instruction pointer is still manipulated
using a postincrement, and is of union mips_instruction type. Since the
union is sized to the largest member (a word), but microMIPS
instructions are a mix of halfword and word sizes, the function does not
always iterate correctly, ending up misaligned with the instruction
stream and interpreting it incorrectly.

Since the instruction modifying the stack pointer is usually the first
in the function, that one is usually handled correctly. But the
instruction which saves the return address to the sp is some variable
number of instructions into the frame and is frequently missed due to
not being on a word boundary, leading to incomplete walking of the
stack.

Fix this by incrementing the instruction pointer based on the size of
the previously decoded instruction (& remove the hack introduced by
commit 34c2f668d0f6b ("MIPS: microMIPS: Add unaligned access support.")
which adjusts the instruction pointer in the case of a 16bit sp move
instruction, but not any other).

Fixes: 34c2f668d0f6b ("MIPS: microMIPS: Add unaligned access support.")
Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
Cc: Marcin Nowakowski <marcin.nowakowski@...tec.com>
Cc: James Hogan <james.hogan@...tec.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Paul Burton <paul.burton@...tec.com>
Cc: linux-mips@...ux-mips.org
Cc: linux-kernel@...r.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/16953/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/mips/kernel/process.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -375,6 +375,7 @@ static int get_frame_info(struct mips_fr
 	bool is_mmips = IS_ENABLED(CONFIG_CPU_MICROMIPS);
 	union mips_instruction insn, *ip, *ip_end;
 	const unsigned int max_insns = 128;
+	unsigned int last_insn_size = 0;
 	unsigned int i;

 	info->pc_offset = -1;
@@ -386,15 +387,19 @@ static int get_frame_info(struct mips_fr

 	ip_end = (void *)ip + info->func_size;

-	for (i = 0; i < max_insns && ip < ip_end; i++, ip++) {
+	for (i = 0; i < max_insns && ip < ip_end; i++) {
+		ip = (void *)ip + last_insn_size;
 		if (is_mmips && mm_insn_16bit(ip->halfword[0])) {
 			insn.halfword[0] = 0;
 			insn.halfword[1] = ip->halfword[0];
+			last_insn_size = 2;
 		} else if (is_mmips) {
 			insn.halfword[0] = ip->halfword[1];
 			insn.halfword[1] = ip->halfword[0];
+			last_insn_size = 4;
 		} else {
 			insn.word = ip->word;
+			last_insn_size = 4;
 		}

 		if (is_jump_ins(&insn))
@@ -416,8 +421,6 @@ static int get_frame_info(struct mips_fr
 						tmp = (ip->halfword[0] >> 1);
 						info->frame_size = -(signed short)(tmp & 0xf);
 					}
-					ip = (void *) &ip->halfword[1];
-					ip--;
 				} else
 #endif
 				info->frame_size = - ip->i_format.simmediate;