Avoid gcc 9.1 strncpy(3) warnings (#447)

Recent GCC releases have warnings related to common strncpy(3) bugs.
These warnings can be avoided by explicitly NUL-terminating the buffer
or using memcpy(3) when the intention is to copy just the characters
without the NUL terminator.

This commit fixes the following warnings:

  [1/27] Compiling C object 'test/9f86d08@@test_syscalls@exe/test_syscalls.c.o'.
  In function ‘test_socket’,
      inlined from ‘main’ at ../test/test_syscalls.c:1899:9:
  ../test/test_syscalls.c:1760:2: warning: ‘strncpy’ output may be truncated copying 108 bytes from a string of length 1023 [-Wstringop-truncation]
   1760 |  strncpy(su.sun_path, testsock, sizeof(su.sun_path));
        |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  [2/27] Compiling C object 'lib/76b5a35@@fuse3@sha/fuse.c.o'.
  ../lib/fuse.c: In function ‘add_name’:
  ../lib/fuse.c:968:2: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
    968 |  strncpy(s, name, len);
        |  ^~~~~~~~~~~~~~~~~~~~~
  ../lib/fuse.c:944:15: note: length computed here
    944 |  size_t len = strlen(name);
        |               ^~~~~~~~~~~~
  [3/27] Compiling C object 'lib/76b5a35@@fuse3@sha/fuse_lowlevel.c.o'.
  ../lib/fuse_lowlevel.c: In function ‘fuse_add_direntry’:
  ../lib/fuse_lowlevel.c:288:2: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
    288 |  strncpy(dirent->name, name, namelen);
        |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ../lib/fuse_lowlevel.c:276:12: note: length computed here
    276 |  namelen = strlen(name);
        |            ^~~~~~~~~~~~
  ../lib/fuse_lowlevel.c: In function ‘fuse_add_direntry_plus’:
  ../lib/fuse_lowlevel.c:381:2: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
    381 |  strncpy(dirent->name, name, namelen);
        |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ../lib/fuse_lowlevel.c:366:12: note: length computed here
    366 |  namelen = strlen(name);
        |            ^~~~~~~~~~~~

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/lib/fuse.c b/lib/fuse.c
index ec6cc59b9fdfa8c51f17c7bc87038a1a1d00b0e7..317abac2ab099cd3ad31d82ba902c0f5ee570a0f 100755 (executable)
--- a/lib/fuse.c
+++ b/lib/fuse.c
@@ -965,7 +965,7 @@ static char *add_name(char **buf, unsigned *bufsize, char *s, const char *name)
                *bufsize = newbufsize;
        }
        s -= len;
-       strncpy(s, name, len);
+       memcpy(s, name, len);
        s--;
        *s = '/';
 

diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index b9f128f68e5edd141c022993360e07aea9ecf507..918893e9aada2fdf734614cb7e6301bc8849125f 100644 (file)
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -285,7 +285,7 @@ size_t fuse_add_direntry(fuse_req_t req, char *buf, size_t bufsize,
        dirent->off = off;
        dirent->namelen = namelen;
        dirent->type = (stbuf->st_mode & S_IFMT) >> 12;
-       strncpy(dirent->name, name, namelen);
+       memcpy(dirent->name, name, namelen);
        memset(dirent->name + namelen, 0, entlen_padded - entlen);
 
        return entlen_padded;
@@ -378,7 +378,7 @@ size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
        dirent->off = off;
        dirent->namelen = namelen;
        dirent->type = (e->attr.st_mode & S_IFMT) >> 12;
-       strncpy(dirent->name, name, namelen);
+       memcpy(dirent->name, name, namelen);
        memset(dirent->name + namelen, 0, entlen_padded - entlen);
 
        return entlen_padded;

diff --git a/test/test_syscalls.c b/test/test_syscalls.c
index 1d776fd740321d5d9a3d7d85ff21ff2208cc9697..e1dbab3a9f86f8fe704a0d3da2c4db4dd148a4fe 100644 (file)
--- a/test/test_syscalls.c
+++ b/test/test_syscalls.c
@@ -1757,7 +1757,8 @@ static int test_socket(void)
                return -1;
        }
        su.sun_family = AF_UNIX;
-       strncpy(su.sun_path, testsock, sizeof(su.sun_path));
+       strncpy(su.sun_path, testsock, sizeof(su.sun_path) - 1);
+       su.sun_path[sizeof(su.sun_path) - 1] = '\0';
        res = bind(fd, (struct sockaddr*)&su, sizeof(su));
        if (res == -1) {
                PERROR("bind");