linux-kernel - [PATCH 3.16 154/202] x86/a.out: Clear the dump structure initially

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Message-ID: <lsq.1556377989.647550654@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Michael Matz" <matz@...e.de>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Borislav Petkov" <bp@...e.de>, x86@...nel.org,
        "Derek Robson" <robsonde@...il.com>
Subject: [PATCH 3.16 154/202] x86/a.out: Clear the dump structure initially

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

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

From: Borislav Petkov <bp@...e.de>

commit 10970e1b4be9c74fce8ab6e3c34a7d718f063f2c upstream.

dump_thread32() in aout_core_dump() does not clear the user32 structure
allocated on the stack as the first thing on function entry.

As a result, the dump.u_comm, dump.u_ar0 and dump.signal which get
assigned before the clearing, get overwritten.

Rename that function to fill_dump() to make it clear what it does and
call it first thing.

This was caught while staring at a patch by Derek Robson
<robsonde@...il.com>.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Derek Robson <robsonde@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael Matz <matz@...e.de>
Cc: x86@...nel.org
Link: https://lkml.kernel.org/r/20190202005512.3144-1-robsonde@gmail.com
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/ia32/ia32_aout.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -50,7 +50,7 @@ static unsigned long get_dr(int n)
 /*
  * fill in the user structure for a core dump..
  */
-static void dump_thread32(struct pt_regs *regs, struct user32 *dump)
+static void fill_dump(struct pt_regs *regs, struct user32 *dump)
 {
 	u32 fs, gs;
 	memset(dump, 0, sizeof(*dump));
@@ -156,10 +156,12 @@ static int aout_core_dump(struct coredum
 	fs = get_fs();
 	set_fs(KERNEL_DS);
 	has_dumped = 1;
+
+	fill_dump(cprm->regs, &dump);
+
 	strncpy(dump.u_comm, current->comm, sizeof(current->comm));
 	dump.u_ar0 = offsetof(struct user32, regs);
 	dump.signal = cprm->siginfo->si_signo;
-	dump_thread32(cprm->regs, &dump);
 
 	/*
 	 * If the size of the dump file exceeds the rlimit, then see