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| author | Eric Biggers <ebiggers@google.com> | 2018-04-17 22:07:06 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-04-29 12:33:10 +0300 |
| commit | c7a936b1dd0f75727b776479f739236a05317f7b (patch) | |
| tree | 4e4605f01c50f5b8967b20132535c1a04d124916 /net/dns_resolver | |
| parent | a370d8a3aaf268896eabaf510e1e8ca4b7ea0a34 (diff) | |
| download | linux-c7a936b1dd0f75727b776479f739236a05317f7b.tar.xz | |
KEYS: DNS: limit the length of option strings
[ 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>
Diffstat (limited to 'net/dns_resolver')
| -rw-r--r-- | net/dns_resolver/dns_key.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c index e1d4d898a007..f0252768ecf4 100644 --- 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_preparsed_payload *prep) 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_preparsed_payload *prep) } 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); } |