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: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Muhammad Bilal --- net/netfilter/nf_conntrack_irc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_irc.c index 522183b9a..9a7b8f622 100644 --- a/net/netfilter/nf_conntrack_irc.c +++ b/net/netfilter/nf_conntrack_irc.c @@ -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; -- 2.54.0