fs: initialize struct nameidata::last

The last member is normally written by link_path_walk(), before being
read by __lookup_hash, among others.

In the special case of calling open() on "/", link_path_walk() will
terminate early without setting the last member, leading __d_alloc
called by __lookup_hash to read uninitialized memory.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20240304190038.3486881-41-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/fs.c b/fs/fs.c
index 0ff7f1b6f9..acd89dd1c9 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -1631,6 +1631,7 @@ struct filename {
 
 static void set_nameidata(struct nameidata *p, struct filename *name)
 {
+	p->last = slash_name;
 	p->stack = p->internal;
 	p->name = name;
 	p->total_link_count = 0;