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netfilter: nf_conntrack_irc: fix parse_dcc() off-by-one OOB read

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parse_dcc() treats data_end as an inclusive end pointer, but its only
caller passes data_limit = ib_ptr + datalen, which points one past the
last valid byte.

The newline search loop iterates while tmp <= data_end, so when no
newline is present, *tmp is read at tmp == data_end, one byte beyond
the region filled by skb_header_pointer().

irc_buffer is kmalloc'd as MAX_SEARCH_SIZE + 1 bytes and datalen is
capped at MAX_SEARCH_SIZE, so the stray read does not fault.  The byte
is uninitialized or stale; if it contains an ASCII digit, simple_strtoul
will consume it and produce a wrong DCC IP or port in the conntrack
expectation.  The extra allocation byte is also a fragile guard: if the
cap or allocation size changes, this becomes a real out-of-bounds read.

Change the loop and its post-loop check to use strict less-than,
consistent with the caller's exclusive-end convention.  Update the
function comment accordingly.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Muhammad Bilal
2026-05-19 17:23:28 -04:00
committed by Florian Westphal
parent d738feccb9
commit ef6400ca25
1 changed files with 3 additions and 3 deletions
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6
net/netfilter/nf_conntrack_irc.c
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@@ -59,7 +59,7 @@ static const char *const dccprotos[] = {
/* tries to get the ip_addr and port out of a dcc command
* return value: -1 on failure, 0 on success
* data pointer to first byte of DCC command data
* data_end pointer to last byte of dcc command data
* data_end one past end of data
* ip returns parsed ip of dcc command
* port returns parsed port of dcc command
* ad_beg_p returns pointer to first byte of addr data
@@ -77,10 +77,10 @@ static int parse_dcc(char *data, const char *data_end, __be32 *ip,
/* Make sure we have a newline character within the packet boundaries
* because simple_strtoul parses until the first invalid character. */
for (tmp = data; tmp <= data_end; tmp++)
for (tmp = data; tmp < data_end; tmp++)
if (*tmp == '\n')
break;
if (tmp > data_end || *tmp != '\n')
if (tmp >= data_end || *tmp != '\n')
return -1;
*ad_beg_p = data;