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fbdevhw: Support symbolic links in fbdev_open 

Resolve symbolic links before the PCI device check in fbdev_open.
Otherwise, opening device files that are symbolic links will fail.

Fixes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1419

Signed-off-by: Moritz Bruder <muesli4@gmail.com>
This commit is contained in:
Moritz Bruder 2022-12-17 18:19:57 +01:00 committed by Matt Turner
parent 5c8f70a17c
commit a8e41a8190
1 changed files with 43 additions and 1 deletions
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44
hw/xfree86/fbdevhw/fbdevhw.c
View File

@ -304,6 +304,31 @@ fbdev_open_pci(struct pci_device *pPci, char **namep)
return -1;
}
/* *
* Try to resolve a filename as symbolic link. If the file is not a link, the
* original filename is returned. NULL is returned if readlink raised an
* error.
*/
static const char *
resolve_link(const char *filename, char *resolve_buf, size_t resolve_buf_size)
{
ssize_t len = readlink(filename, resolve_buf, resolve_buf_size - 1);
/* if it is a link resolve it */
if (len >= 0) {
resolve_buf[len] = '\0';
return resolve_buf;
}
else {
if (errno == EINVAL) {
return filename;
}
else {
// Have caller handle error condition.
return NULL;
}
}
}
static int
fbdev_open(int scrnIndex, const char *dev, char **namep)
{
@ -331,9 +356,26 @@ fbdev_open(int scrnIndex, const char *dev, char **namep)
/* only touch non-PCI devices on this path */
{
char device_path_buf[PATH_MAX];
char buf[PATH_MAX] = {0};
char *sysfs_path = NULL;
char *node = strrchr(dev, '/') + 1;
char const *real_dev = resolve_link(dev, device_path_buf,
sizeof(device_path_buf));
if (real_dev == NULL) {
xf86DrvMsg(scrnIndex, X_ERROR,
"Failed resolving symbolic link for device '%s': %s",
dev, strerror(errno));
return -1;
}
const char *node = strrchr(real_dev, '/');
if (node == NULL) {
node = real_dev;
}
else {
node++;
}
if (asprintf(&sysfs_path, "/sys/class/graphics/%s", node) < 0 ||
readlink(sysfs_path, buf, sizeof(buf) - 1) < 0 ||