The unbounded %[] here made me look at the kernel, where the size of a
block device name is limited to 32 bytes (including the NUL), so
although the 1024 bytes of toybuf was plenty, that meant that the
32-byte buffer for "/dev/%s" was too small because the "%s" alone could
require the entire buffer. Fix that, and simplify the code a bit by only
using toybuf for the fgets(). I didn't switch to fscanf() because the
file has two lines of headers, and calling fgets() twice to skip the
header seemed more awkward than keeping the continue in the loop.
---
toys/other/blkid.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
From bb59b4620b3a6392fe4dd210468b3ee29ef4a273 Mon Sep 17 00:00:00 2001
From: Elliott Hughes <[email protected]>
Date: Fri, 24 Sep 2021 17:51:47 -0700
Subject: [PATCH] blkid: more scanf fun.
The unbounded %[] here made me look at the kernel, where the size of a
block device name is limited to 32 bytes (including the NUL), so
although the 1024 bytes of toybuf was plenty, that meant that the
32-byte buffer for "/dev/%s" was too small because the "%s" alone could
require the entire buffer. Fix that, and simplify the code a bit by only
using toybuf for the fgets(). I didn't switch to fscanf() because the
file has two lines of headers, and calling fgets() twice to skip the
header seemed more awkward than keeping the continue in the loop.
---
toys/other/blkid.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/toys/other/blkid.c b/toys/other/blkid.c
index e3badca7..01b5971b 100644
--- a/toys/other/blkid.c
+++ b/toys/other/blkid.c
@@ -197,12 +197,11 @@ void blkid_main(void)
if (*toys.optargs && !FLAG(L) && !FLAG(U)) loopfiles(toys.optargs, do_blkid);
else {
unsigned int ma, mi, sz, fd;
- char *name = toybuf, *buffer = toybuf+1024, device[32];
+ char name[32], device[5+32];
FILE *fp = xfopen("/proc/partitions", "r");
- while (fgets(buffer, 1024, fp)) {
- *name = 0;
- if (sscanf(buffer, " %u %u %u %[^\n ]", &ma, &mi, &sz, name) != 4)
+ while (fgets(toybuf, sizeof(toybuf), fp)) {
+ if (sscanf(toybuf, " %u %u %u %31s", &ma, &mi, &sz, name) != 4)
continue;
sprintf(device, "/dev/%.20s", name);
--
2.33.0.685.g46640cef36-goog
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