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-rw-r--r--lib/lib.c34
1 files changed, 25 insertions, 9 deletions
diff --git a/lib/lib.c b/lib/lib.c
index 955960ca..b0ac4715 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -447,22 +447,38 @@ off_t fdlength(int fd)
// note: for existing buffers use len = size-1, will set buf[len] = 0
char *readfileat(int dirfd, char *name, char *ibuf, off_t *plen)
{
- off_t len = *plen-!!ibuf;
+ off_t len, rlen;
int fd;
- char *buf;
+ char *buf, *rbuf;
+
+ // Unsafe to probe for size with a supplied buffer, don't ever do that.
+ if (CFG_TOYBOX_DEBUG && (ibuf ? !*plen : *plen)) error_exit("bad readfileat");
if (-1 == (fd = openat(dirfd, name, O_RDONLY))) return 0;
- if (!len) {
- len = fdlength(fd);
- // proc files don't report a length, so try 1 page minimum.
- if (len<4096) len = 4096;
- }
+
+ // If we dunno the length, probe it. If we can't probe, start with 1 page.
+ if (!*plen) {
+ if ((len = fdlength(fd))>0) *plen = len;
+ else len = 4096;
+ } else len = *plen-1;
+
if (!ibuf) buf = xmalloc(len+1);
else buf = ibuf;
- *plen = len = readall(fd, buf, len);
+ for (rbuf = buf;;) {
+ rlen = readall(fd, rbuf, len);
+ if (*plen || rlen<len) break;
+
+ // If reading unknown size, expand buffer by 1.5 each time we fill it up.
+ rlen += rbuf-buf;
+ buf = xrealloc(buf, len = (rlen*3)/2);
+ rbuf = buf+rlen;
+ len -= rlen;
+ }
+ *plen = len = rlen+(buf-ibuf);
close(fd);
- if (len<0) {
+
+ if (rlen<0) {
if (ibuf != buf) free(buf);
buf = 0;
} else buf[len] = 0;