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

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: ae3b7361dc ("afs: Fix validation/callback interaction")
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
Marc Dionne 2019-01-09 17:23:54 +00:00 committed by David Howells
parent 5edc22cc1d
commit 4882a27cec
1 changed files with 0 additions and 1 deletions
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1
fs/afs/inode.c
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@ -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;
}