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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, Mark Rutland <mark.rutland@arm.com>,
	Eric Biggers <ebiggers@google.com>,
	"David S. Miller" <davem@davemloft.net>
Subject: [PATCH 3.18 10/24] KEYS: DNS: limit the length of option strings
Date: Fri, 27 Apr 2018 15:57:45 +0200	[thread overview]
Message-ID: <20180427135632.006035787@linuxfoundation.org> (raw)
In-Reply-To: <20180427135631.584839868@linuxfoundation.org>

3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Eric Biggers <ebiggers@google.com>


[ Upstream commit 9c438d7a3a52dcc2b9ed095cb87d3a5e83cf7e60 ]

Adding a dns_resolver key whose payload contains a very long option name
resulted in that string being printed in full.  This hit the WARN_ONCE()
in set_precision() during the printk(), because printk() only supports a
precision of up to 32767 bytes:

    precision 1000000 too large
    WARNING: CPU: 0 PID: 752 at lib/vsprintf.c:2189 vsnprintf+0x4bc/0x5b0

Fix it by limiting option strings (combined name + value) to a much more
reasonable 128 bytes.  The exact limit is arbitrary, but currently the
only recognized option is formatted as "dnserror=%lu" which fits well
within this limit.

Also ratelimit the printks.

Reproducer:

    perl -e 'print "#", "A" x 1000000, "\x00"' | keyctl padd dns_resolver desc @s

This bug was found using syzkaller.

Reported-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 4a2d789267e0 ("DNS: If the DNS server returns an error, allow that to be cached [ver #2]")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/dns_resolver/dns_key.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -25,6 +25,7 @@
 #include <linux/moduleparam.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/ratelimit.h>
 #include <linux/kernel.h>
 #include <linux/keyctl.h>
 #include <linux/err.h>
@@ -91,9 +92,9 @@ dns_resolver_preparse(struct key_prepars
 
 			next_opt = memchr(opt, '#', end - opt) ?: end;
 			opt_len = next_opt - opt;
-			if (!opt_len) {
-				printk(KERN_WARNING
-				       "Empty option to dns_resolver key\n");
+			if (opt_len <= 0 || opt_len > 128) {
+				pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n",
+						    opt_len);
 				return -EINVAL;
 			}
 
@@ -127,10 +128,8 @@ dns_resolver_preparse(struct key_prepars
 			}
 
 		bad_option_value:
-			printk(KERN_WARNING
-			       "Option '%*.*s' to dns_resolver key:"
-			       " bad/missing value\n",
-			       opt_nlen, opt_nlen, opt);
+			pr_warn_ratelimited("Option '%*.*s' to dns_resolver key: bad/missing value\n",
+					    opt_nlen, opt_nlen, opt);
 			return -EINVAL;
 		} while (opt = next_opt + 1, opt < end);
 	}

  parent reply	other threads:[~2018-04-27 13:58 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27 13:57 [PATCH 3.18 00/24] 3.18.107-stable review Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 01/24] cifs: do not allow creating sockets except with SMB1 posix exensions Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 02/24] x86/tsc: Prevent 32bit truncation in calc_hpet_ref() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 03/24] ext4: fix deadlock between inline_data and ext4_expand_extra_isize_ea() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 04/24] ext4: bugfix for mmaped pages in mpage_release_unused_pages() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 05/24] ext4: dont update checksum of new initialized bitmaps Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 06/24] perf: Return proper values for user stack errors Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 07/24] mm/filemap.c: fix NULL pointer in page_cache_tree_insert() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 08/24] jbd2: fix use after free in kjournald2() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 09/24] bonding: do not set slave_dev npinfo before slave_enable_netpoll in bond_enslave Greg Kroah-Hartman
2018-04-27 13:57 ` Greg Kroah-Hartman [this message]
2018-04-27 13:57 ` [PATCH 3.18 11/24] l2tp: check sockaddr length in pppol2tp_connect() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 12/24] tcp: dont read out-of-bounds opsize Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 13/24] team: avoid adding twice the same option to the event list Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 14/24] team: fix netconsole setup over team Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 15/24] pppoe: check sockaddr length in pppoe_connect() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 16/24] llc: hold llc_sap before release_sock() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 17/24] llc: fix NULL pointer deref for SOCK_ZAPPED Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 18/24] packet: fix bitfield update race Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 19/24] tcp: md5: reject TCP_MD5SIG or TCP_MD5SIG_EXT on established sockets Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 20/24] net: af_packet: fix race in PACKET_{R|T}X_RING Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 21/24] llc: delete timers synchronously in llc_sk_free() Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 22/24] ipv6: add RTA_TABLE and RTA_PREFSRC to rtm_ipv6_policy Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 23/24] scsi: mptsas: Disable WRITE SAME Greg Kroah-Hartman
2018-04-27 13:57 ` [PATCH 3.18 24/24] cdrom: information leak in cdrom_ioctl_media_changed() Greg Kroah-Hartman
2018-04-27 16:00 ` [PATCH 3.18 00/24] 3.18.107-stable review Dede Dindin Qudsy
2018-04-28  5:51   ` Greg Kroah-Hartman
2018-04-28  6:40     ` Harsh Shandilya
2018-04-27 18:12 ` Shuah Khan
2018-04-28  5:02   ` Greg Kroah-Hartman
2018-04-27 19:03 ` kernelci.org bot
2018-04-27 19:41 ` Theodore Y. Ts'o
2018-04-28  4:35   ` Greg Kroah-Hartman
2018-04-27 21:33 ` Harsh Shandilya
2018-04-28  5:02   ` Greg Kroah-Hartman
2018-04-28 14:24 ` Guenter Roeck

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