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authorJakub Kicinski <jakub.kicinski@netronome.com>2018-07-17 14:32:24 -0700
committerDavid S. Miller <davem@davemloft.net>2018-07-18 15:24:04 -0700
commitf15f084ff11519172c67fac4dde61daf4e9ad345 (patch)
treeecf317e3e5924b4a3fdc3f4fe6ca534eb8f68e3d /Documentation
parent088cbac6bea4d383b9e01f042b50fe00898714f5 (diff)
downloadlinux-f15f084ff11519172c67fac4dde61daf4e9ad345.tar.gz
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>
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