talexander
/
freebsd_amp_hwpstate
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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
This commit is contained in:
Dag-Erling Smørgrav 2024-05-10 23:15:54 +02:00
parent 4d09eb87c5
commit 25945af47e
1 changed files with 30 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
libexec/tftpd/tftpd.c
View File

@ -611,12 +611,20 @@ tftp_rrq(int peer, char *recvbuffer, size_t size)
static int
find_next_name(char *filename, int *fd)
{
int i;
time_t tval;
size_t len;
struct tm lt;
char yyyymmdd[MAXPATHLEN];
/*
* 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, namelen;
struct tm lt;
/* 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, &lt);
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;
}