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pktgen: convert safe uses of strncpy() to strcpy() to avoid string truncation warning 

GCC 8 complains:

net/core/pktgen.c: In function ‘pktgen_if_write’:
net/core/pktgen.c:1419:4: warning: ‘strncpy’ output may be truncated copying between 0 and 31 bytes from a string of length 127 [-Wstringop-truncation]
    strncpy(pkt_dev->src_max, buf, len);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/core/pktgen.c:1399:4: warning: ‘strncpy’ output may be truncated copying between 0 and 31 bytes from a string of length 127 [-Wstringop-truncation]
    strncpy(pkt_dev->src_min, buf, len);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/core/pktgen.c:1290:4: warning: ‘strncpy’ output may be truncated copying between 0 and 31 bytes from a string of length 127 [-Wstringop-truncation]
    strncpy(pkt_dev->dst_max, buf, len);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/core/pktgen.c:1268:4: warning: ‘strncpy’ output may be truncated copying between 0 and 31 bytes from a string of length 127 [-Wstringop-truncation]
    strncpy(pkt_dev->dst_min, buf, len);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is no bug here, but the code is not perfect either.  It copies
sizeof(pkt_dev->/member/) - 1 from user space into buf, and then does
a strcmp(pkt_dev->/member/, buf) hence assuming buf will be null-terminated
and shorter than pkt_dev->/member/ (pkt_dev->/member/ is never
explicitly null-terminated, and strncpy() doesn't have to null-terminate
so the assumption must be on buf).  The use of strncpy() without explicit
null-termination looks suspicious.  Convert to use straight strcpy().

strncpy() would also null-pad the output, but that's clearly unnecessary
since the author calls memset(pkt_dev->/member/, 0, sizeof(..)); prior
to strncpy(), anyway.

While at it format the code for "dst_min", "dst_max", "src_min" and
"src_max" in the same way by removing extra new lines in one case.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2018-07-17 14:32:24 -07:00 committed by David S. Miller
parent 088cbac6be
commit f15f084ff1
1 changed files with 4 additions and 6 deletions
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10
net/core/pktgen.c
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@ -1265,7 +1265,7 @@ static ssize_t pktgen_if_write(struct file *file,
buf[len] = 0;
if (strcmp(buf, pkt_dev->dst_min) != 0) {
memset(pkt_dev->dst_min, 0, sizeof(pkt_dev->dst_min));
strncpy(pkt_dev->dst_min, buf, len);
strcpy(pkt_dev->dst_min, buf);
pkt_dev->daddr_min = in_aton(pkt_dev->dst_min);
pkt_dev->cur_daddr = pkt_dev->daddr_min;
}
@ -1280,14 +1280,12 @@ static ssize_t pktgen_if_write(struct file *file,
if (len < 0)
return len;
if (copy_from_user(buf, &user_buffer[i], len))
return -EFAULT;
buf[len] = 0;
if (strcmp(buf, pkt_dev->dst_max) != 0) {
memset(pkt_dev->dst_max, 0, sizeof(pkt_dev->dst_max));
strncpy(pkt_dev->dst_max, buf, len);
strcpy(pkt_dev->dst_max, buf);
pkt_dev->daddr_max = in_aton(pkt_dev->dst_max);
pkt_dev->cur_daddr = pkt_dev->daddr_max;
}
@ -1396,7 +1394,7 @@ static ssize_t pktgen_if_write(struct file *file,
buf[len] = 0;
if (strcmp(buf, pkt_dev->src_min) != 0) {
memset(pkt_dev->src_min, 0, sizeof(pkt_dev->src_min));
strncpy(pkt_dev->src_min, buf, len);
strcpy(pkt_dev->src_min, buf);
pkt_dev->saddr_min = in_aton(pkt_dev->src_min);
pkt_dev->cur_saddr = pkt_dev->saddr_min;
}
@ -1416,7 +1414,7 @@ static ssize_t pktgen_if_write(struct file *file,
buf[len] = 0;
if (strcmp(buf, pkt_dev->src_max) != 0) {
memset(pkt_dev->src_max, 0, sizeof(pkt_dev->src_max));
strncpy(pkt_dev->src_max, buf, len);
strcpy(pkt_dev->src_max, buf);
pkt_dev->saddr_max = in_aton(pkt_dev->src_max);
pkt_dev->cur_saddr = pkt_dev->saddr_max;
}