From 0307d16f3610eb29ad0b7529846de7d62fed60ca Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 18 Mar 2025 11:20:19 +0000 Subject: [PATCH] afs: Fix afs_atcell_get_link() to check if ws_cell is unset first Fix afs_atcell_get_link() to check if the workstation cell is unset before doing the RCU pathwalk bit where we dereference that. Fixes: 823869e1e616 ("afs: Fix afs_atcell_get_link() to handle RCU pathwalk") Reported-by: syzbot+76a6f18e3af82e84f264@syzkaller.appspotmail.com Signed-off-by: David Howells Link: https://lore.kernel.org/r/2481796.1742296819@warthog.procyon.org.uk Tested-by: syzbot+76a6f18e3af82e84f264@syzkaller.appspotmail.com cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Signed-off-by: Christian Brauner --- fs/afs/dynroot.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c index 008698d706caa..7d997f7a80284 100644 --- a/fs/afs/dynroot.c +++ b/fs/afs/dynroot.c @@ -314,6 +314,9 @@ static const char *afs_atcell_get_link(struct dentry *dentry, struct inode *inod const char *name; bool dotted = vnode->fid.vnode == 3; + if (!rcu_access_pointer(net->ws_cell)) + return ERR_PTR(-ENOENT); + if (!dentry) { /* We're in RCU-pathwalk. */ cell = rcu_dereference(net->ws_cell); @@ -325,9 +328,6 @@ static const char *afs_atcell_get_link(struct dentry *dentry, struct inode *inod return name; } - if (!rcu_access_pointer(net->ws_cell)) - return ERR_PTR(-ENOENT); - down_read(&net->cells_lock); cell = rcu_dereference_protected(net->ws_cell, lockdep_is_held(&net->cells_lock)); -- 2.39.5