linux-kernel - [PATCH 5.14 021/100] profiling: fix shift-out-of-bounds bugs

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Date:   Fri, 24 Sep 2021 14:43:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Pavel Skripkin <paskripkin@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        syzbot+e68c89a9510c159d9684@...kaller.appspotmail.com
Subject: [PATCH 5.14 021/100] profiling: fix shift-out-of-bounds bugs

From: Pavel Skripkin <paskripkin@...il.com>

commit 2d186afd04d669fe9c48b994c41a7405a3c9f16d upstream.

Syzbot reported shift-out-of-bounds bug in profile_init().
The problem was in incorrect prof_shift. Since prof_shift value comes from
userspace we need to clamp this value into [0, BITS_PER_LONG -1]
boundaries.

Second possible shiht-out-of-bounds was found by Tetsuo:
sample_step local variable in read_profile() had "unsigned int" type,
but prof_shift allows to make a BITS_PER_LONG shift. So, to prevent
possible shiht-out-of-bounds sample_step type was changed to
"unsigned long".

Also, "unsigned short int" will be sufficient for storing
[0, BITS_PER_LONG] value, that's why there is no need for
"unsigned long" prof_shift.

Link: https://lkml.kernel.org/r/20210813140022.5011-1-paskripkin@gmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-and-tested-by: syzbot+e68c89a9510c159d9684@...kaller.appspotmail.com
Suggested-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/profile.c |   21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -41,7 +41,8 @@ struct profile_hit {
 #define NR_PROFILE_GRP		(NR_PROFILE_HIT/PROFILE_GRPSZ)
 
 static atomic_t *prof_buffer;
-static unsigned long prof_len, prof_shift;
+static unsigned long prof_len;
+static unsigned short int prof_shift;
 
 int prof_on __read_mostly;
 EXPORT_SYMBOL_GPL(prof_on);
@@ -67,8 +68,8 @@ int profile_setup(char *str)
 		if (str[strlen(sleepstr)] == ',')
 			str += strlen(sleepstr) + 1;
 		if (get_option(&str, &par))
-			prof_shift = par;
-		pr_info("kernel sleep profiling enabled (shift: %ld)\n",
+			prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
+		pr_info("kernel sleep profiling enabled (shift: %u)\n",
 			prof_shift);
 #else
 		pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
@@ -78,21 +79,21 @@ int profile_setup(char *str)
 		if (str[strlen(schedstr)] == ',')
 			str += strlen(schedstr) + 1;
 		if (get_option(&str, &par))
-			prof_shift = par;
-		pr_info("kernel schedule profiling enabled (shift: %ld)\n",
+			prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
+		pr_info("kernel schedule profiling enabled (shift: %u)\n",
 			prof_shift);
 	} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
 		prof_on = KVM_PROFILING;
 		if (str[strlen(kvmstr)] == ',')
 			str += strlen(kvmstr) + 1;
 		if (get_option(&str, &par))
-			prof_shift = par;
-		pr_info("kernel KVM profiling enabled (shift: %ld)\n",
+			prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
+		pr_info("kernel KVM profiling enabled (shift: %u)\n",
 			prof_shift);
 	} else if (get_option(&str, &par)) {
-		prof_shift = par;
+		prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
 		prof_on = CPU_PROFILING;
-		pr_info("kernel profiling enabled (shift: %ld)\n",
+		pr_info("kernel profiling enabled (shift: %u)\n",
 			prof_shift);
 	}
 	return 1;
@@ -468,7 +469,7 @@ read_profile(struct file *file, char __u
 	unsigned long p = *ppos;
 	ssize_t read;
 	char *pnt;
-	unsigned int sample_step = 1 << prof_shift;
+	unsigned long sample_step = 1UL << prof_shift;
 
 	profile_flip_buffers();
 	if (p >= (prof_len+1)*sizeof(unsigned int))