path: root/net/dns_resolver
diff options
authorEric Biggers <ebiggers@google.com>2018-04-17 12:07:06 -0700
committerDavid S. Miller <davem@davemloft.net>2018-04-17 15:17:41 -0400
commit9c438d7a3a52dcc2b9ed095cb87d3a5e83cf7e60 (patch)
tree1e4203f8ae5469aae5b7478f3f3c92f4c3c14e65 /net/dns_resolver
parentsfc: check RSS is active for filter insert (diff)
KEYS: DNS: limit the length of option strings
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>
Diffstat (limited to 'net/dns_resolver')
1 files changed, 5 insertions, 7 deletions
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
index 8396705deffc..40c851693f77 100644
--- a/net/dns_resolver/dns_key.c
+++ b/net/dns_resolver/dns_key.c
@@ -91,9 +91,9 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
next_opt = memchr(opt, '#', end - opt) ?: end;
opt_len = next_opt - opt;
- if (!opt_len) {
- "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 +127,8 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
- "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);