netdev - [PATCH net 1/4] nfp: don't pad strings in nfp_cpp_resource

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Date:   Mon, 11 Jun 2018 21:33:35 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH net 1/4] nfp: don't pad strings in nfp_cpp_resource_find() to avoid gcc 8 warning

Once upon a time nfp_cpp_resource_find() took a name parameter,
which could be any user-chosen string.  Resources are identified
by a CRC32 hash of a 8 byte string, so we had to pad user input
with zeros to make sure CRC32 gave the correct result.

Since then nfp_cpp_resource_find() was made to operate on allocated
resources only (struct nfp_resource).  We kzalloc those so there is
no need to pad the strings and use memcmp.

This avoids a GCC 8 stringop-truncation warning:

In function ‘nfp_cpp_resource_find’,
    inlined from ‘nfp_resource_try_acquire’ at .../nfpcore/nfp_resource.c:153:8,
    inlined from ‘nfp_resource_acquire’ at .../nfpcore/nfp_resource.c:206:9:
    .../nfpcore/nfp_resource.c:108:2: warning:  strncpy’ output may be truncated copying 8 bytes from a string of length 8 [-Wstringop-truncation]
      strncpy(name_pad, res->name, sizeof(name_pad));
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@...ronome.com>
---
 drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c
index 2dd89dba9311..d32af598da90 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c
@@ -98,21 +98,18 @@ struct nfp_resource {
 
 static int nfp_cpp_resource_find(struct nfp_cpp *cpp, struct nfp_resource *res)
 {
-	char name_pad[NFP_RESOURCE_ENTRY_NAME_SZ] = {};
 	struct nfp_resource_entry entry;
 	u32 cpp_id, key;
 	int ret, i;
 
 	cpp_id = NFP_CPP_ID(NFP_RESOURCE_TBL_TARGET, 3, 0);  /* Atomic read */
 
-	strncpy(name_pad, res->name, sizeof(name_pad));
-
 	/* Search for a matching entry */
-	if (!memcmp(name_pad, NFP_RESOURCE_TBL_NAME "\0\0\0\0\0\0\0\0", 8)) {
+	if (!strcmp(res->name, NFP_RESOURCE_TBL_NAME)) {
 		nfp_err(cpp, "Grabbing device lock not supported\n");
 		return -EOPNOTSUPP;
 	}
-	key = crc32_posix(name_pad, sizeof(name_pad));
+	key = crc32_posix(res->name, NFP_RESOURCE_ENTRY_NAME_SZ);
 
 	for (i = 0; i < NFP_RESOURCE_TBL_ENTRIES; i++) {
 		u64 addr = NFP_RESOURCE_TBL_BASE +
-- 
2.17.1