[PATCH] prevent unlinking moved symlinks

[PATCH] prevent unlinking moved symlinks

[John K Luebs]

Here's a fairly obvious fix; so someone please check it carefully.

This patch causes the remove handler to check that each symlink
actually points to the correct devnode and skip it if it does not.
The current policy for symlinks in devnode add handling is to "move" the
link if it exists, so when an old devnode is being removed its stored
symlink entries might be stale.

Signed-off-by: John K. Luebs <jkluebs@luebsphoto.com>

diff -pur udev-054/udev_remove.c udev-054-new/udev_remove.c
--- udev-054/udev_remove.c	2005-02-25 22:18:21.000000000 -0500
+++ udev-054-new/udev_remove.c	2005-03-08 00:13:46.000000000 -0500
@@ -90,6 +90,31 @@ static int delete_node(struct udevice *u
 		return -1;
 	}
 
+	foreach_strpart(udev->symlink, " ", pos, len) {
+		char linkname[NAME_SIZE];
+		char linkpath[NAME_SIZE];
+
+		strfieldcpymax(linkname, pos, len+1);
+		snprintf(linkpath, NAME_SIZE, "%s/%s", udev_root, linkname);
+		linkpath[NAME_SIZE-1] = '\0';
+
+		if ((stat(linkpath, &stats) != 0) || (stats.st_rdev != udev->devt))
+			continue;
+
+		dbg("unlinking symlink '%s'", linkpath);
+		retval = unlink(linkpath);
+		if (errno = ENOENT)
+			retval = 0;
+		if (retval) {
+			dbg("unlink(%s) failed with error '%s'",
+				linkpath, strerror(errno));
+			return retval;
+		}
+		if (strchr(udev->symlink, '/')) {
+			delete_path(linkpath);
+		}
+	}
+
 	info("removing device node '%s'", filename);
 	retval = unlink_secure(filename);
 	if (retval)
@@ -114,27 +139,6 @@ static int delete_node(struct udevice *u
 	if (strchr(udev->name, '/'))
 		delete_path(filename);
 
-	foreach_strpart(udev->symlink, " ", pos, len) {
-		char linkname[NAME_SIZE];
-
-		strfieldcpymax(linkname, pos, len+1);
-		snprintf(filename, NAME_SIZE, "%s/%s", udev_root, linkname);
-		filename[NAME_SIZE-1] = '\0';
-
-		dbg("unlinking symlink '%s'", filename);
-		retval = unlink(filename);
-		if (errno = ENOENT)
-			retval = 0;
-		if (retval) {
-			dbg("unlink(%s) failed with error '%s'",
-				filename, strerror(errno));
-			return retval;
-		}
-		if (strchr(udev->symlink, '/')) {
-			delete_path(filename);
-		}
-	}
-
 	return retval;
 }
 



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Re: [PATCH] prevent unlinking moved symlinks

[Kay Sievers]

On Tue, 2005-03-08 at 00:59 -0500, John K Luebs wrote:
> Here's a fairly obvious fix; so someone please check it carefully.
> 
> This patch causes the remove handler to check that each symlink
> actually points to the correct devnode and skip it if it does not.
> The current policy for symlinks in devnode add handling is to "move" the
> link if it exists, so when an old devnode is being removed its stored
> symlink entries might be stale.

That's a nice change. I've applied that to my tree.

Thanks,
Kay



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