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| author | Eric Biggers <ebiggers@google.com> | 2018-04-17 21:07:06 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-04-17 21:17:41 +0200 |
| commit | 9c438d7a3a52dcc2b9ed095cb87d3a5e83cf7e60 (patch) | |
| tree | 1e4203f8ae5469aae5b7478f3f3c92f4c3c14e65 /net/dns_resolver | |
| parent | sfc: check RSS is active for filter insert (diff) | |
| download | linux-9c438d7a3a52dcc2b9ed095cb87d3a5e83cf7e60.tar.xz linux-9c438d7a3a52dcc2b9ed095cb87d3a5e83cf7e60.zip | |
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')
| -rw-r--r-- | net/dns_resolver/dns_key.c | 12 |
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) { - 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 +127,8 @@ 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); } |