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tcp, tcp_splice: Get rid of false positive CWE-394 Coverity warning from fls()

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We use the return value of fls() as array index for debug strings.

While fls() can return -1 (if no bit is set), Coverity Scan doesn't
see that we're first checking the return value of another fls() call
with the same bitmask, before using it.

Call fls() once, store its return value, check it, and use the stored
value as array index.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Stefano Brivio 2023-02-27 02:45:42 +01:00
parent a48c5c2abf
commit 5474bc5485
2 changed files with 24 additions and 12 deletions
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12
tcp.c
View File

@ -743,15 +743,19 @@ static void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
unsigned long flag)
{
if (flag & (flag - 1)) {
int flag_index = fls(~flag);
if (!(conn->flags & ~flag))
return;
conn->flags &= flag;
if (fls(~flag) >= 0) {
if (flag_index >= 0) {
debug("TCP: index %li: %s dropped", CONN_IDX(conn),
tcp_flag_str[fls(~flag)]);
tcp_flag_str[flag_index]);
}
} else {
int flag_index = fls(~flag);
if (conn->flags & flag) {
/* Special case: setting ACK_FROM_TAP_DUE on a
* connection where it's already set is used to
@ -766,9 +770,9 @@ static void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
}
conn->flags |= flag;
if (fls(flag) >= 0) {
if (flag_index >= 0) {
debug("TCP: index %li: %s", CONN_IDX(conn),
tcp_flag_str[fls(flag)]);
tcp_flag_str[flag_index]);
}
}

24
tcp_splice.c
View File

@ -127,22 +127,26 @@ static void conn_flag_do(const struct ctx *c, struct tcp_splice_conn *conn,
unsigned long flag)
{
if (flag & (flag - 1)) {
int flag_index = fls(~flag);
if (!(conn->flags & ~flag))
return;
conn->flags &= flag;
if (fls(~flag) >= 0) {
if (flag_index >= 0) {
debug("TCP (spliced): index %li: %s dropped", CONN_IDX(conn),
tcp_splice_flag_str[fls(~flag)]);
tcp_splice_flag_str[flag_index]);
}
} else {
int flag_index = fls(flag);
if (conn->flags & flag)
return;
conn->flags |= flag;
if (fls(flag) >= 0) {
if (flag_index >= 0) {
debug("TCP (spliced): index %li: %s", CONN_IDX(conn),
tcp_splice_flag_str[fls(flag)]);
tcp_splice_flag_str[flag_index]);
}
}
@ -207,22 +211,26 @@ static void conn_event_do(const struct ctx *c, struct tcp_splice_conn *conn,
unsigned long event)
{
if (event & (event - 1)) {
int flag_index = fls(~event);
if (!(conn->events & ~event))
return;
conn->events &= event;
if (fls(~event) >= 0) {
if (flag_index >= 0) {
debug("TCP (spliced): index %li, ~%s", CONN_IDX(conn),
tcp_splice_event_str[fls(~event)]);
tcp_splice_event_str[flag_index]);
}
} else {
int flag_index = fls(event);
if (conn->events & event)
return;
conn->events |= event;
if (fls(event) >= 0) {
if (flag_index >= 0) {
debug("TCP (spliced): index %li, %s", CONN_IDX(conn),
tcp_splice_event_str[fls(event)]);
tcp_splice_event_str[flag_index]);
}
}