[PATCH net] tipc: check msg->req data len in tipc_nl_compat_bearer_disable

[Xin Long]

This patch is to fix an uninit-value issue, reported by syzbot:

  BUG: KMSAN: uninit-value in memchr+0xce/0x110 lib/string.c:981
  Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x191/0x1f0 lib/dump_stack.c:113
    kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
    __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
    memchr+0xce/0x110 lib/string.c:981
    string_is_valid net/tipc/netlink_compat.c:176 [inline]
    tipc_nl_compat_bearer_disable+0x2a1/0x480 net/tipc/netlink_compat.c:449
    __tipc_nl_compat_doit net/tipc/netlink_compat.c:327 [inline]
    tipc_nl_compat_doit+0x3ac/0xb00 net/tipc/netlink_compat.c:360
    tipc_nl_compat_handle net/tipc/netlink_compat.c:1178 [inline]
    tipc_nl_compat_recv+0x1b1b/0x27b0 net/tipc/netlink_compat.c:1281

TLV_GET_DATA_LEN() may return a negtive int value, which will be
used as size_t (becoming a big unsigned long) passed into memchr,
cause this issue.

Similar to what it does in tipc_nl_compat_bearer_enable(), this
fix is to return -EINVAL when TLV_GET_DATA_LEN() is negtive in
tipc_nl_compat_bearer_disable(), as well as in
tipc_nl_compat_link_stat_dump() and tipc_nl_compat_link_reset_stats().

Reported-by: syzbot+30eaa8bf392f7faff...@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien....@gmail.com>
---
 net/tipc/netlink_compat.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
index c6a04c0..cf15506 100644
--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -445,7 +445,11 @@ static int tipc_nl_compat_bearer_disable(struct 
tipc_nl_compat_cmd_doit *cmd,
        if (!bearer)
                return -EMSGSIZE;
 
-       len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_BEARER_NAME);
+       len = TLV_GET_DATA_LEN(msg->req);
+       if (len <= 0)
+               return -EINVAL;
+
+       len = min_t(int, len, TIPC_MAX_BEARER_NAME);
        if (!string_is_valid(name, len))
                return -EINVAL;
 
@@ -539,7 +543,11 @@ static int tipc_nl_compat_link_stat_dump(struct 
tipc_nl_compat_msg *msg,
 
        name = (char *)TLV_DATA(msg->req);
 
-       len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+       len = TLV_GET_DATA_LEN(msg->req);
+       if (len <= 0)
+               return -EINVAL;
+
+       len = min_t(int, len, TIPC_MAX_BEARER_NAME);
        if (!string_is_valid(name, len))
                return -EINVAL;
 
@@ -817,7 +825,11 @@ static int tipc_nl_compat_link_reset_stats(struct 
tipc_nl_compat_cmd_doit *cmd,
        if (!link)
                return -EMSGSIZE;
 
-       len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+       len = TLV_GET_DATA_LEN(msg->req);
+       if (len <= 0)
+               return -EINVAL;
+
+       len = min_t(int, len, TIPC_MAX_BEARER_NAME);
        if (!string_is_valid(name, len))
                return -EINVAL;
 
-- 
2.1.0