afs: Don't set vnode->cb_s_break in afs_validate()

Marc Dionne · dhowells · commit 4882a27cec24 · 2019-01-17T15:15:52.000Z
A cb_interest record is not necessarily attached to the vnode on entry to afs_validate(), which can cause an oops when we try to bring the vnode's cb_s_break up to date in the default case (ie. no current callback promise and the vnode has not been deleted). Fix this by simply removing the line, as vnode->cb_s_break will be set when needed by afs_register_server_cb_interest() when we next get a callback promise from RPC call. The oops looks something like: BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 ... RIP: 0010:afs_validate+0x66/0x250 [kafs] ... Call Trace: afs_d_revalidate+0x8d/0x340 [kafs] ? __d_lookup+0x61/0x150 lookup_dcache+0x44/0x70 ? lookup_dcache+0x44/0x70 __lookup_hash+0x24/0xa0 do_unlinkat+0x11d/0x2c0 __x64_sys_unlink+0x23/0x30 do_syscall_64+0x4d/0xf0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fixes: ae3b736 ("afs: Fix validation/callback interaction") Signed-off-by: Marc Dionne <marc.dionne@auristor.com> Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
@@ -414,7 +414,6 @@ int afs_validate(struct afs_vnode *vnode, struct key *key)
 	} else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
 		valid = true;
 	} else {
-		vnode->cb_s_break = vnode->cb_interest->server->cb_s_break;
 		vnode->cb_v_break = vnode->volume->cb_v_break;
 		valid = false;
 	}

Original file line number	Diff line number	Diff line change
`@@ -414,7 +414,6 @@ int afs_validate(struct afs_vnode vnode, struct key key)`
`414`	`414`	`} else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {`
`415`	`415`	`valid = true;`
`416`	`416`	`} else {`
`417`		`- vnode->cb_s_break = vnode->cb_interest->server->cb_s_break;`
`418`	`417`	`vnode->cb_v_break = vnode->volume->cb_v_break;`
`419`	`418`	`valid = false;`
`420`	`419`	`}`