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afs: Fix afs_atcell_get_link() to check if ws_cell is unset first

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Fix afs_atcell_get_link() to check if the workstation cell is unset before
doing the RCU pathwalk bit where we dereference that.

Fixes: 823869e1e6 ("afs: Fix afs_atcell_get_link() to handle RCU pathwalk")
Reported-by: syzbot+76a6f18e3af82e84f264@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/2481796.1742296819@warthog.procyon.org.uk
Tested-by: syzbot+76a6f18e3af82e84f264@syzkaller.appspotmail.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
David Howells 2025-03-18 11:20:19 +00:00 committed by Christian Brauner
parent 4701f33a10
commit 0307d16f36
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GPG key ID: 91C61BC06578DCA2
1 changed files with 3 additions and 3 deletions
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6
fs/afs/dynroot.c
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@ -314,6 +314,9 @@ static const char *afs_atcell_get_link(struct dentry *dentry, struct inode *inod
const char *name; const char *name;
bool dotted = vnode->fid.vnode == 3; bool dotted = vnode->fid.vnode == 3;
if (!rcu_access_pointer(net->ws_cell))
return ERR_PTR(-ENOENT);
if (!dentry) { if (!dentry) {
/* We're in RCU-pathwalk. */ /* We're in RCU-pathwalk. */
cell = rcu_dereference(net->ws_cell); 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; return name;
} }
if (!rcu_access_pointer(net->ws_cell))
return ERR_PTR(-ENOENT);
down_read(&net->cells_lock); down_read(&net->cells_lock);
cell = rcu_dereference_protected(net->ws_cell, lockdep_is_held(&net->cells_lock)); cell = rcu_dereference_protected(net->ws_cell, lockdep_is_held(&net->cells_lock));