linux-kernel - [PATCH 1/3] compat sysinfo(2): don't bother with field-by-field copyout

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Message-Id: <20200529001023.4107547-1-viro@ZenIV.linux.org.uk>
Date:   Fri, 29 May 2020 01:10:21 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH 1/3] compat sysinfo(2): don't bother with field-by-field copyout

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 kernel/sys.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index d325f3ab624a..b4a0324a0699 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2634,6 +2634,7 @@ struct compat_sysinfo {
 COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
 {
 	struct sysinfo s;
+	struct compat_sysinfo s_32;
 
 	do_sysinfo(&s);
 
@@ -2658,23 +2659,23 @@ COMPAT_SYSCALL_DEFINE1(sysinfo, struct compat_sysinfo __user *, info)
 		s.freehigh >>= bitcount;
 	}
 
-	if (!access_ok(info, sizeof(struct compat_sysinfo)) ||
-	    __put_user(s.uptime, &info->uptime) ||
-	    __put_user(s.loads[0], &info->loads[0]) ||
-	    __put_user(s.loads[1], &info->loads[1]) ||
-	    __put_user(s.loads[2], &info->loads[2]) ||
-	    __put_user(s.totalram, &info->totalram) ||
-	    __put_user(s.freeram, &info->freeram) ||
-	    __put_user(s.sharedram, &info->sharedram) ||
-	    __put_user(s.bufferram, &info->bufferram) ||
-	    __put_user(s.totalswap, &info->totalswap) ||
-	    __put_user(s.freeswap, &info->freeswap) ||
-	    __put_user(s.procs, &info->procs) ||
-	    __put_user(s.totalhigh, &info->totalhigh) ||
-	    __put_user(s.freehigh, &info->freehigh) ||
-	    __put_user(s.mem_unit, &info->mem_unit))
+	memset(&s_32, 0, sizeof(s_32));
+	s_32.uptime = s.uptime;
+	s_32.loads[0] = s.loads[0];
+	s_32.loads[1] = s.loads[1];
+	s_32.loads[2] = s.loads[2];
+	s_32.totalram = s.totalram;
+	s_32.freeram = s.freeram;
+	s_32.sharedram = s.sharedram;
+	s_32.bufferram = s.bufferram;
+	s_32.totalswap = s.totalswap;
+	s_32.freeswap = s.freeswap;
+	s_32.procs = s.procs;
+	s_32.totalhigh = s.totalhigh;
+	s_32.freehigh = s.freehigh;
+	s_32.mem_unit = s.mem_unit;
+	if (copy_to_user(info, &s_32, sizeof(s_32)))
 		return -EFAULT;
-
 	return 0;
 }
 #endif /* CONFIG_COMPAT */
-- 
2.11.0