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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Matteo Croce <mcroce@microsoft.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Petr Mladek <pmladek@suse.com>, Arnd Bergmann <arnd@arndb.de>,
        Mike Rapoport <rppt@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        Robin Holt <robinmholt@gmail.com>,
        Fabian Frederick <fabf@skynet.be>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: [PATCH 4.19 098/101] Revert "kernel/reboot.c: convert simple_strtoul to kstrtoint"
Date:   Tue, 17 Nov 2020 14:06:05 +0100
Message-Id: <20201117122117.909452999@linuxfoundation.org>
In-Reply-To: <20201117122113.128215851@linuxfoundation.org>
References: <20201117122113.128215851@linuxfoundation.org>
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From: Matteo Croce <mcroce@microsoft.com>

commit 8b92c4ff4423aa9900cf838d3294fcade4dbda35 upstream.

Patch series "fix parsing of reboot= cmdline", v3.

The parsing of the reboot= cmdline has two major errors:

 - a missing bound check can crash the system on reboot

 - parsing of the cpu number only works if specified last

Fix both.

This patch (of 2):

This reverts commit 616feab753972b97.

kstrtoint() and simple_strtoul() have a subtle difference which makes
them non interchangeable: if a non digit character is found amid the
parsing, the former will return an error, while the latter will just
stop parsing, e.g.  simple_strtoul("123xyx") = 123.

The kernel cmdline reboot= argument allows to specify the CPU used for
rebooting, with the syntax `s####` among the other flags, e.g.
"reboot=warm,s31,force", so if this flag is not the last given, it's
silently ignored as well as the subsequent ones.

Fixes: 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint")
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Robin Holt <robinmholt@gmail.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201103214025.116799-2-mcroce@linux.microsoft.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[sudip: use reboot_mode instead of mode]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/reboot.c |   21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -539,22 +539,15 @@ static int __init reboot_setup(char *str
 			break;
 
 		case 's':
-		{
-			int rc;
-
-			if (isdigit(*(str+1))) {
-				rc = kstrtoint(str+1, 0, &reboot_cpu);
-				if (rc)
-					return rc;
-			} else if (str[1] == 'm' && str[2] == 'p' &&
-				   isdigit(*(str+3))) {
-				rc = kstrtoint(str+3, 0, &reboot_cpu);
-				if (rc)
-					return rc;
-			} else
+			if (isdigit(*(str+1)))
+				reboot_cpu = simple_strtoul(str+1, NULL, 0);
+			else if (str[1] == 'm' && str[2] == 'p' &&
+							isdigit(*(str+3)))
+				reboot_cpu = simple_strtoul(str+3, NULL, 0);
+			else
 				reboot_mode = REBOOT_SOFT;
 			break;
-		}
+
 		case 'g':
 			reboot_mode = REBOOT_GPIO;
 			break;