afs: Fix afs_dynroot_readdir() to not use the RCU read lock

afs_dynroot_readdir() uses the RCU read lock to walk the cell list whilst
emitting cell automount entries - but dir_emit() may write to a userspace
buffer, thereby causing a fault to occur and waits to happen.

Fix afs_dynroot_readdir() to get a shared lock on net->cells_lock instead.

This can be triggered by enabling lockdep, preconfiguring a number of
cells, doing "mount -t afs none /afs -o dyn" (or using the kafs-client
package with afs.mount systemd unit enabled) and then doing "ls /afs".

Fixes: 1d0b929fc070 ("afs: Change dynroot to create contents on demand")
Reported-by: [email protected]
Reported-by: [email protected]
Reported-by: [email protected]
Reported-by: [email protected]
Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/[email protected]
cc: Marc Dionne <[email protected]>
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

0 files changed, 0 insertions, 0 deletions