Commit c9d6b287 authored Jan 15, 2020 by Rasmus Villemoes Committed by Greg Kroah-Hartman Jan 22, 2020

devtmpfs: fix theoretical stale pointer deref in devtmpfsd()

After complete(&setup_done), devtmpfs_init proceeds and may actually
return, invalidating the *err pointer, before devtmpfsd() proceeds to
reading back *err.

This is of course completely theoretical since the error conditions
never trigger in practice, and even if they did, nobody cares about
the exit value from a kernel thread, so it doesn't matter if we happen
to read back some garbage from some other stack frame. Still, this
isn't a pattern that should be copy-pasted, so fix it.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20200115184154.3492-2-linux@rasmusvillemoes.dk

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 0707cfa5

drivers/base/devtmpfs.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -390,12 +390,13 @@ static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,

		static int devtmpfsd(void *p)
		{
		int *err = p;
		*err = ksys_unshare(CLONE_NEWNS);
		if (*err)
		int err;

		err = ksys_unshare(CLONE_NEWNS);
		if (err)
		goto out;
		*err = do_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
		if (*err)
		err = do_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
		if (err)
		goto out;
		ksys_chdir("/.."); /* will traverse into overmounted root */
		ksys_chroot(".");
		@@ -421,8 +422,9 @@ static int devtmpfsd(void *p)
		}
		return 0;
		out:
		(int )p = err;
		complete(&setup_done);
		return *err;
		return err;
		}

		/*

Admin message