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mtd: fix use-after-free in find_ubi_for_mtd (segfault on musl arm64) #171

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Merged
widgetii merged 1 commit into from
Jun 2, 2026
Merged

mtd: fix use-after-free in find_ubi_for_mtd (segfault on musl arm64) #171

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26 changes: 15 additions & 11 deletions src/mtd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,7 @@ int find_ubi_for_mtd(int mtd_num) {
DIR *d = opendir("/sys/class/ubi");
if (!d)
return -1;
int ubi_num = -1;
struct dirent *de;
while ((de = readdir(d))) {
if (strncmp(de->d_name, "ubi", 3) != 0)
Expand All @@ -134,20 +135,23 @@ int find_ubi_for_mtd(int mtd_num) {
char path[128];
snprintf(path, sizeof(path), "/sys/class/ubi/%s/mtd_num", de->d_name);
FILE *f = fopen(path, "r");
if (f) {
int num;
if (fscanf(f, "%d", &num) == 1 && num == mtd_num) {
fclose(f);
closedir(d);
int ubi_num;
sscanf(de->d_name, "ubi%d", &ubi_num);
return ubi_num;
}
fclose(f);
if (!f)
continue;
int num;
bool match = fscanf(f, "%d", &num) == 1 && num == mtd_num;
fclose(f);
if (match) {
/* Parse the number BEFORE closedir(): POSIX leaves the
* dirent invalid after closedir, and musl actively
* invalidates it (where glibc happens to keep it alive),
* so reading de->d_name after closedir is a segfault on
* the aarch64 musl build. */
sscanf(de->d_name, "ubi%d", &ubi_num);
break;
}
}
closedir(d);
return -1;
return ubi_num;
}

int enum_ubi_volumes(int ubi_num, ubi_vol_info_t *vols, int max_vols) {
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