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authorMax Reitz <mreitz@redhat.com>2017-07-17 17:12:07 +0200
committerKevin Wolf <kwolf@redhat.com>2017-07-18 15:14:36 +0200
commit7c8730d45f63b76588da5ea0d4eff73a0bcae188 (patch)
tree9f2dd0021e6be78d79b9982ed63e85d1b76c1fe6
parentf80256b7eebfbe20683b3a2b2720ad9991313761 (diff)
block/vvfat: Fix compiler warning with gcc 7
gcc 7 complains that the sprintf() might write a null byte beyond the end of the tail buffer. That is wrong, but we can silence it by making i unsigned (it can never be negative anyway, see the if condition right before). For some reason, this allows gcc to suddenly accurately calculate the range of i so we can give the tail[] array the exact size it needs to have (which is 8 bytes) without gcc complaining. In addition, let us convert the sprintf() to snprintf(), because that is always nicer, and add an assertion about the range of the return value afterwards so we can see that "8 - len" will never be negative and thus "entry->name + MIN(j, 8 - len)" will never be out of bounds. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/vvfat.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/block/vvfat.c b/block/vvfat.c
index 6b11596abf..a9e207f7f0 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -549,7 +549,7 @@ static direntry_t *create_short_filename(BDRVVVFATState *s,
const gchar *p, *last_dot = NULL;
gunichar c;
bool lossy_conversion = false;
- char tail[11];
+ char tail[8];
if (!entry) {
return NULL;
@@ -614,7 +614,8 @@ static direntry_t *create_short_filename(BDRVVVFATState *s,
for (i = lossy_conversion ? 1 : 0; i < 999999; i++) {
direntry_t *entry1;
if (i > 0) {
- int len = sprintf(tail, "~%d", i);
+ int len = snprintf(tail, sizeof(tail), "~%u", (unsigned)i);
+ assert(len <= 7);
memcpy(entry->name + MIN(j, 8 - len), tail, len);
}
for (entry1 = array_get(&(s->directory), directory_start);