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tipc: avoid possible string overflow

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gcc points out that the combined length of the fixed-length inputs to
l->name is larger than the destination buffer size:

net/tipc/link.c: In function 'tipc_link_create':
net/tipc/link.c:465:26: error: '%s' directive writing up to 32 bytes
into a region of size between 26 and 58 [-Werror=format-overflow=]
sprintf(l->name, "%s:%s-%s:unknown", self_str, if_name, peer_str);

net/tipc/link.c:465:2: note: 'sprintf' output 11 or more bytes
(assuming 75) into a destination of size 60
sprintf(l->name, "%s:%s-%s:unknown", self_str, if_name, peer_str);

A detailed analysis reveals that the theoretical maximum length of
a link name is:
max self_str + 1 + max if_name + 1 + max peer_str + 1 + max if_name =
16 + 1 + 15 + 1 + 16 + 1 + 15 = 65
Since we also need space for a trailing zero we now set MAX_LINK_NAME
to 68.

Just to be on the safe side we also replace the sprintf() call with
snprintf().

Fixes: 25b0b9c4e8 ("tipc: handle collisions of 32-bit node address
hash values")
Reported-by: Arnd Bergmann <arnd@arndb.de>

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jon Maloy 2018-03-29 23:20:45 +02:00 committed by David S. Miller
parent 7a74d39cc2
commit 7494cfa6d3
2 changed files with 3 additions and 2 deletions
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2
include/uapi/linux/tipc.h
View File

@ -216,7 +216,7 @@ struct tipc_group_req {
#define TIPC_MAX_MEDIA_NAME 16
#define TIPC_MAX_IF_NAME 16
#define TIPC_MAX_BEARER_NAME 32
#define TIPC_MAX_LINK_NAME 60
#define TIPC_MAX_LINK_NAME 68
#define SIOCGETLINKNAME SIOCPROTOPRIVATE

3
net/tipc/link.c
View File

@ -462,7 +462,8 @@ bool tipc_link_create(struct net *net, char *if_name, int bearer_id,
sprintf(peer_str, "%x", peer);
}
/* Peer i/f name will be completed by reset/activate message */
sprintf(l->name, "%s:%s-%s:unknown", self_str, if_name, peer_str);
snprintf(l->name, sizeof(l->name), "%s:%s-%s:unknown",
self_str, if_name, peer_str);
strcpy(l->if_name, if_name);
l->addr = peer;