kernel/linux.git/fs/afs/vl_alias.c, branch linux-7.1.y

afs: Fix dynamic lookup to fail on cell lookup failure

2025-10-29T12:51:38+00:00

When a process tries to access an entry in /afs, normally what happens is that an automount dentry is created by ->lookup() and then triggered, which jumps through the ->d_automount() op. Currently, afs_dynroot_lookup() does not do cell DNS lookup, leaving that to afs_d_automount() to perform - however, it is possible to use access() or stat() on the automount point, which will always return successfully, have briefly created an afs_cell record if one did not already exist. This means that something like: test -d "/afs/.west" && echo Directory exists will print "Directory exists" even though no such cell is configured. This breaks the "west" python module available on PIP as it expects this access to fail. Now, it could be possible to make afs_dynroot_lookup() perform the DNS[*] lookup, but that would make "ls --color /afs" do this for each cell in /afs that is listed but not yet probed. kafs-client, probably wrongly, preloads the entire cell database and all the known cells are then listed in /afs - and doing ls /afs would be very, very slow, especially if any cell supplied addresses but was wholly inaccessible. [*] When I say "DNS", actually read getaddrinfo(), which could use any one of a host of mechanisms. Could also use static configuration. To fix this, make the following changes: (1) Create an enum to specify the origination point of a call to afs_lookup_cell() and pass this value into that function in place of the "excl" parameter (which can be derived from it). There are six points of origination: - Cell preload through /proc/net/afs/cells - Root cell config through /proc/net/afs/rootcell - Lookup in dynamic root - Automount trigger - Direct mount with mount() syscall - Alias check where YFS tells us the cell name is different (2) Add an extra state into the afs_cell state machine to indicate a cell that's been initialised, but not yet looked up. This is separate from one that can be considered active and has been looked up at least once. (3) Make afs_lookup_cell() vary its behaviour more, depending on where it was called from: If called from preload or root cell config, DNS lookup will not happen until we definitely want to use the cell (dynroot mount, automount, direct mount or alias check). The cell will appear in /afs but stat() won't trigger DNS lookup. If the cell already exists, dynroot will not wait for the DNS lookup to complete. If the cell did not already exist, dynroot will wait. If called from automount, direct mount or alias check, it will wait for the DNS lookup to complete. (4) Make afs_lookup_cell() return an error if lookup failed in one way or another. We try to return -ENOENT if the DNS says the cell does not exist and -EDESTADDRREQ if we couldn't access the DNS. Reported-by: Markus Suvanto Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220685 Signed-off-by: David Howells Link: https://patch.msgid.link/1784747.1761158912@warthog.procyon.org.uk Fixes: 1d0b929fc070 ("afs: Change dynroot to create contents on demand") Tested-by: Markus Suvanto cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner

afs: Drop the net parameter from afs_unuse_cell()

2025-03-10T09:47:15+00:00

Remove the redundant net parameter to afs_unuse_cell() as cell->net can be used instead. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-12-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-8-dhowells@redhat.com/ # v4

afs: Make afs_lookup_cell() take a trace note

2025-03-10T09:47:15+00:00

Pass a note to be added to the afs_cell tracepoint to afs_lookup_cell() so that different callers can be distinguished. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/20250224234154.2014840-11-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20250310094206.801057-7-dhowells@redhat.com/ # v4

afs: Fix the maximum cell name length

2025-01-07T14:55:25+00:00

The kafs filesystem limits the maximum length of a cell to 256 bytes, but a problem occurs if someone actually does that: kafs tries to create a directory under /proc/net/afs/ with the name of the cell, but that fails with a warning: WARNING: CPU: 0 PID: 9 at fs/proc/generic.c:405 because procfs limits the maximum filename length to 255. However, the DNS limits the maximum lookup length and, by extension, the maximum cell name, to 255 less two (length count and trailing NUL). Fix this by limiting the maximum acceptable cellname length to 253. This also allows us to be sure we can create the "/afs/./" mountpoint too. Further, split the YFS VL record cell name maximum to be the 256 allowed by the protocol and ignore the record retrieved by YFSVL.GetCellName if it exceeds 253. Fixes: c3e9f888263b ("afs: Implement client support for the YFSVL.GetCellName RPC op") Reported-by: syzbot+7848fee1f1e5c53f912b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/6776d25d.050a0220.3a8527.0048.GAE@google.com/ Signed-off-by: David Howells Link: https://lore.kernel.org/r/376236.1736180460@warthog.procyon.org.uk Tested-by: syzbot+7848fee1f1e5c53f912b@syzkaller.appspotmail.com cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Christian Brauner

afs: Defer volume record destruction to a workqueue

2024-01-01T16:37:27+00:00

Defer volume record destruction to a workqueue so that afs_put_volume() isn't going to run the destruction process in the callback workqueue whilst the server is holding up other clients whilst waiting for us to reply to a CB.CallBack notification RPC. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

afs: Make it possible to find the volumes that are using a server

2024-01-01T16:37:27+00:00

Make it possible to find the afs_volume structs that are using an afs_server struct to aid in breaking volume callbacks. The way this is done is that each afs_volume already has an array of afs_server_entry records that point to the servers where that volume might be found. An afs_volume backpointer and a list node is added to each entry and each entry is then added to an RCU-traversable list on the afs_server to which it points. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

afs: Keep a record of the current fileserver endpoint state

2024-01-01T16:37:27+00:00

Keep a record of the current fileserver endpoint state, including the probe state, and replace it when a new probe is started rather than just squelching the old state and overwriting it. Clearance of the old state can cause a race if there's another thread also currently trying to communicate with that server. It appears that this race might be the culprit for some occasions where kafs complains about invalid data in the RPC reply because the rotation algorithm fell all the way through without actually issuing an RPC call and the error return got filled in from the probe state (which has a zero error recorded). Whatever happens to be in the caller's reply buffer is then taken as the response. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

afs: Simplify error handling

2023-12-24T15:22:53+00:00

Simplify error handling a bit by moving it from the afs_addr_cursor struct to the afs_operation and afs_vl_cursor structs and using the error prioritisation function for accumulating errors from multiple sources (AFS tries to rotate between multiple fileservers, some of which may be inaccessible or in some state of offlinedness). Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

rxrpc, afs: Allow afs to pin rxrpc_peer objects

2023-12-24T15:22:50+00:00

Change rxrpc's API such that: (1) A new function, rxrpc_kernel_lookup_peer(), is provided to look up an rxrpc_peer record for a remote address and a corresponding function, rxrpc_kernel_put_peer(), is provided to dispose of it again. (2) When setting up a call, the rxrpc_peer object used during a call is now passed in rather than being set up by rxrpc_connect_call(). For afs, this meenat passing it to rxrpc_kernel_begin_call() rather than the full address (the service ID then has to be passed in as a separate parameter). (3) A new function, rxrpc_kernel_remote_addr(), is added so that afs can get a pointer to the transport address for display purposed, and another, rxrpc_kernel_remote_srx(), to gain a pointer to the full rxrpc address. (4) The function to retrieve the RTT from a call, rxrpc_kernel_get_srtt(), is then altered to take a peer. This now returns the RTT or -1 if there are insufficient samples. (5) Rename rxrpc_kernel_get_peer() to rxrpc_kernel_call_get_peer(). (6) Provide a new function, rxrpc_kernel_get_peer(), to get a ref on a peer the caller already has. This allows the afs filesystem to pin the rxrpc_peer records that it is using, allowing faster lookups and pointer comparisons rather than comparing sockaddr_rxrpc contents. It also makes it easier to get hold of the RTT. The following changes are made to afs: (1) The addr_list struct's addrs[] elements now hold a peer struct pointer and a service ID rather than a sockaddr_rxrpc. (2) When displaying the transport address, rxrpc_kernel_remote_addr() is used. (3) The port arg is removed from afs_alloc_addrlist() since it's always overridden. (4) afs_merge_fs_addr4() and afs_merge_fs_addr6() do peer lookup and may now return an error that must be handled. (5) afs_find_server() now takes a peer pointer to specify the address. (6) afs_find_server(), afs_compare_fs_alists() and afs_merge_fs_addr[46]{} now do peer pointer comparison rather than address comparison. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org

afs: Turn the afs_addr_list address array into an array of structs

2023-12-24T15:22:50+00:00

Turn the afs_addr_list address array into an array of structs, thereby allowing per-address (such as RTT) info to be added. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org