The branch main has been updated by des:
URL:
https://cgit.FreeBSD.org/src/commit/?id=25945af47e7a1d06c44c8c160045a866e90569ab
commit 25945af47e7a1d06c44c8c160045a866e90569ab
Author: Dag-Erling Smørgrav <d...@freebsd.org>
AuthorDate: 2024-05-10 21:15:54 +0000
Commit: Dag-Erling Smørgrav <d...@freebsd.org>
CommitDate: 2024-05-10 21:16:26 +0000
tftpd: silence gcc overflow warnings
GCC 13 complains that we might be writing too much to an on-stack buffer
when createing a filename.
In practice there is a check that filename isn't too long given the
time format and other static characters so GCC is incorrect, but GCC
isn't wrong that we're potentially trying to put a MAXPATHLEN length
string + some other characters into a MAXPATHLEN buffer (if you ignore
the check GCC can't realistically evaluate at compile time).
Switch to snprintf to populate filename to ensure that future logic
errors don't result in a stack overflow.
Shorten the questionably named yyyymmdd buffer enough to slience the
warning (checking the snprintf return value isn't sufficent) while
preserving maximum flexibility for admins who use the -F option.
MFC after: 3 days
Sponsored by: Klara, Inc.
Reviewed by: brooks
Differential Revision: https://reviews.freebsd.org/D45086
---
libexec/tftpd/tftpd.c | 43 +++++++++++++++++++++++++++++--------------
1 file changed, 29 insertions(+), 14 deletions(-)
diff --git a/libexec/tftpd/tftpd.c b/libexec/tftpd/tftpd.c
index 80497738f60d..3f67ad2920cf 100644
--- a/libexec/tftpd/tftpd.c
+++ b/libexec/tftpd/tftpd.c
@@ -611,12 +611,20 @@ tftp_rrq(int peer, char *recvbuffer, size_t size)
static int
find_next_name(char *filename, int *fd)
{
- int i;
+ /*
+ * GCC "knows" that we might write all of yyyymmdd plus the static
+ * elemenents in the format into into newname and thus complains
+ * unless we reduce the size. This array is still too big, but since
+ * the format is user supplied, it's not clear what a better limit
+ * value would be and this is sufficent to silence the warnings.
+ */
+ static const int suffix_len = strlen("..00");
+ char yyyymmdd[MAXPATHLEN - suffix_len];
+ char newname[MAXPATHLEN];
+ int i, ret;
time_t tval;
- size_t len;
+ size_t len, namelen;
struct tm lt;
- char yyyymmdd[MAXPATHLEN];
- char newname[MAXPATHLEN];
/* Create the YYYYMMDD part of the filename */
time(&tval);
@@ -624,26 +632,33 @@ find_next_name(char *filename, int *fd)
len = strftime(yyyymmdd, sizeof(yyyymmdd), newfile_format, <);
if (len == 0) {
syslog(LOG_WARNING,
- "Filename suffix too long (%d characters maximum)",
- MAXPATHLEN);
+ "Filename suffix too long (%zu characters maximum)",
+ sizeof(yyyymmdd) - 1);
return (EACCESS);
}
/* Make sure the new filename is not too long */
- if (strlen(filename) > MAXPATHLEN - len - 5) {
+ namelen = strlen(filename);
+ if (namelen >= sizeof(newname) - len - suffix_len) {
syslog(LOG_WARNING,
- "Filename too long (%zd characters, %zd maximum)",
- strlen(filename), MAXPATHLEN - len - 5);
+ "Filename too long (%zu characters, %zu maximum)",
+ namelen,
+ sizeof(newname) - len - suffix_len - 1);
return (EACCESS);
}
/* Find the first file which doesn't exist */
for (i = 0; i < 100; i++) {
- sprintf(newname, "%s.%s.%02d", filename, yyyymmdd, i);
- *fd = open(newname,
- O_WRONLY | O_CREAT | O_EXCL,
- S_IRUSR | S_IWUSR | S_IRGRP |
- S_IWGRP | S_IROTH | S_IWOTH);
+ ret = snprintf(newname, sizeof(newname), "%s.%s.%02d",
+ filename, yyyymmdd, i);
+ /*
+ * Size checked above so this can't happen, we'd use a
+ * (void) cast, but gcc intentionally ignores that if
+ * snprintf has __attribute__((warn_unused_result)).
+ */
+ if (ret < 0 || (size_t)ret >= sizeof(newname))
+ __unreachable();
+ *fd = open(newname, O_WRONLY | O_CREAT | O_EXCL, 0666);
if (*fd > 0)
return 0;
}
