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sd-device: use chase_symlinks() O_PATH fd

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chase_symlinks() can return its last O_PATH fd to us. Let's use that and
make the access() check a bit tighter by going via faccessat() on the
O_PATH fd.

This doesn't really change too much, but is nice in context of the next
commit, which uses the O_PATH fd in one other way.
This commit is contained in:
Lennart Poettering
2022-04-13 14:40:09 +02:00
parent c87c307806
commit 1793bb6112
1 changed files with 18 additions and 13 deletions
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src/libsystemd/sd-device/sd-device.c
+18 -13
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@@ -150,7 +150,9 @@ int device_set_syspath(sd_device *device, const char *_syspath, bool verify) {
_syspath);
if (verify) {
r = chase_symlinks(_syspath, NULL, 0, &syspath, NULL);
_cleanup_close_ int fd = -1;
r = chase_symlinks(_syspath, NULL, 0, &syspath, &fd);
if (r == -ENOENT)
/* the device does not exist (any more?) */
return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
@@ -181,25 +183,28 @@ int device_set_syspath(sd_device *device, const char *_syspath, bool verify) {
path_simplify(syspath);
}
if (path_startswith(syspath, "/sys/devices/")) {
char *path;
if (path_startswith(syspath, "/sys/devices/")) {
/* For proper devices, stricter rules apply: they must have a 'uevent' file,
* otherwise we won't allow them */
/* all 'devices' require an 'uevent' file */
path = strjoina(syspath, "/uevent");
if (access(path, F_OK) < 0) {
if (faccessat(fd, "uevent", F_OK, 0) < 0) {
if (errno == ENOENT)
/* This is not a valid device.
* Note, this condition is quite often satisfied when
* enumerating devices or finding a parent device.
/* This is not a valid device. Note, this condition is quite often
* satisfied when enumerating devices or finding a parent device.
* Hence, use log_trace_errno() here. */
return log_trace_errno(SYNTHETIC_ERRNO(ENODEV),
"sd-device: the uevent file \"%s\" does not exist.", path);
"sd-device: the uevent file \"%s/uevent\" does not exist.", syspath);
return log_debug_errno(errno, "sd-device: cannot access uevent file for %s: %m", syspath);
return log_debug_errno(errno, "sd-device: cannot find uevent file for %s: %m", syspath);
}
} else {
/* everything else just needs to be a directory */
if (!is_dir(syspath, false))
struct stat st;
/* For everything else lax rules apply: they just need to be a directory */
if (fstat(fd, &st) < 0)
return log_debug_errno(errno, "sd-device: failed to check if syspath \"%s\" is a directory: %m", syspath);
if (!S_ISDIR(st.st_mode))
return log_debug_errno(SYNTHETIC_ERRNO(ENODEV),
"sd-device: the syspath \"%s\" is not a directory.", syspath);
}