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sd-device: do no allocate strings of unknown length on the stack

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Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=33881.

Not only we would duplicate unknown input on the stack, we would do it
over and over. So let's first check that the input has reasonable length,
but also allocate just one fixed size buffer.

(cherry picked from commit e17c95af8e450caacde692875b30675cea75211f)
(cherry picked from commit 5172ef4a58bda5be18dcdbbe0abd2c6bb4f08743)
(cherry picked from commit 7e0f374aaca4d964c880d5966811ce2ecfdda94f)
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2021-05-05 16:49:41 +02:00
parent 35067ea801
commit 05f7f883f5
2 changed files with 31 additions and 27 deletions
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54
src/libsystemd/sd-device/sd-device.c
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@ -249,29 +249,31 @@ _public_ int sd_device_new_from_devnum(sd_device **ret, char type, dev_t devnum)
}
_public_ int sd_device_new_from_subsystem_sysname(sd_device **ret, const char *subsystem, const char *sysname) {
char *name, *syspath;
size_t len = 0;
char syspath[PATH_MAX], *name;
assert_return(ret, -EINVAL);
assert_return(subsystem, -EINVAL);
assert_return(sysname, -EINVAL);
assert_return(strlen(sysname) < PATH_MAX - strlen("/sys/bus/"), -ENAMETOOLONG);
if (streq(subsystem, "subsystem")) {
syspath = strjoina("/sys/subsystem/", sysname);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/subsystem/%s", sysname) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
syspath = strjoina("/sys/bus/", sysname);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/bus/%s", sysname) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
syspath = strjoina("/sys/class/", sysname);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/class/%s", sysname) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
} else if (streq(subsystem, "module")) {
syspath = strjoina("/sys/module/", sysname);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/module/%s", sysname) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
} else if (streq(subsystem, "drivers")) {
char subsys[PATH_MAX];
char *driver;
@ -282,39 +284,37 @@ _public_ int sd_device_new_from_subsystem_sysname(sd_device **ret, const char *s
driver[0] = '\0';
driver++;
syspath = strjoina("/sys/subsystem/", subsys, "/drivers/", driver);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/subsystem/%s/drivers/%s", subsys, driver) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
syspath = strjoina("/sys/bus/", subsys, "/drivers/", driver);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/bus/%s/drivers/%s", subsys, driver) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
}
}
/* translate sysname back to sysfs filename */
name = strdupa(sysname);
while (name[len] != '\0') {
if (name[len] == '/')
name[len] = '!';
len++;
}
for (size_t i = 0; name[i]; i++)
if (name[i] == '/')
name[i] = '!';
syspath = strjoina("/sys/subsystem/", subsystem, "/devices/", name);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/subsystem/%s/devices/%s", subsystem, name) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
syspath = strjoina("/sys/bus/", subsystem, "/devices/", name);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/bus/%s/devices/%s", subsystem, name) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
syspath = strjoina("/sys/class/", subsystem, "/", name);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/class/%s/%s", subsystem, name) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
syspath = strjoina("/sys/firmware/", subsystem, "/", sysname);
if (access(syspath, F_OK) >= 0)
if (snprintf_ok(syspath, sizeof syspath, "/sys/firmware/%s/%s", subsystem, sysname) &&
access(syspath, F_OK) >= 0)
return sd_device_new_from_syspath(ret, syspath);
return -ENODEV;

4
test/fuzz/fuzz-journald-kmsg/oss-fuzz-33881 Normal file
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