talos-obmc-linux/fs/afs/security.c, branch v5.0.1

afs: Fix callback handling

2018-10-23T23:41:09+00:00

In some circumstances, the callback interest pointer is NULL, so in such a case we can't dereference it when checking to see if the callback is broken. This causes an oops in some circumstances. Fix this by replacing the function that worked out the aggregate break counter with one that actually does the comparison, and then make that return true (ie. broken) if there is no callback interest as yet (ie. the pointer is NULL). Fixes: 68251f0a6818 ("afs: Fix whole-volume callback handling") Signed-off-by: David Howells

afs: Increase to 64-bit volume ID and 96-bit vnode ID for YFS

2018-10-23T23:41:08+00:00

Increase the sizes of the volume ID to 64 bits and the vnode ID (inode number equivalent) to 96 bits to allow the support of YFS. This requires the iget comparator to check the vnode->fid rather than i_ino and i_generation as i_ino is not sufficiently capacious. It also requires this data to be placed into the vnode cache key for fscache. For the moment, just discard the top 32 bits of the vnode ID when returning it though stat. Signed-off-by: David Howells

afs: Fix directory permissions check

2018-05-16T20:35:23+00:00

Doing faccessat("/afs/some/directory", 0) triggers a BUG in the permissions check code. Fix this by just removing the BUG section. If no permissions are asked for, just return okay if the file exists. Also: (1) Split up the directory check so that it has separate if-statements rather than if-else-if (e.g. checking for MAY_EXEC shouldn't skip the check for MAY_READ and MAY_WRITE). (2) Check for MAY_CHDIR as MAY_EXEC. Without the main fix, the following BUG may occur: kernel BUG at fs/afs/security.c:386! invalid opcode: 0000 [#1] SMP PTI ... RIP: 0010:afs_permission+0x19d/0x1a0 [kafs] ... Call Trace: ? inode_permission+0xbe/0x180 ? do_faccessat+0xdc/0x270 ? do_syscall_64+0x60/0x1f0 ? entry_SYSCALL_64_after_hwframe+0x49/0xbe Fixes: 00d3b7a4533e ("[AFS]: Add security support.") Reported-by: Jonathan Billings Signed-off-by: David Howells

afs: Fix whole-volume callback handling

2018-05-14T14:15:18+00:00

It's possible for an AFS file server to issue a whole-volume notification that callbacks on all the vnodes in the file have been broken. This is done for R/O and backup volumes (which don't have per-file callbacks) and for things like a volume being taken offline. Fix callback handling to detect whole-volume notifications, to track it across operations and to check it during inode validation. Fixes: c435ee34551e ("afs: Overhaul the callback handling") Signed-off-by: David Howells

afs: Make it possible to get the data version in readpage

2018-04-09T20:53:56+00:00

Store the data version number indicated by an FS.FetchData op into the read request structure so that it's accessible by the page reader. Signed-off-by: David Howells

afs: Fix checker warnings

2018-04-09T20:12:31+00:00

Fix warnings raised by checker, including: (*) Warnings raised by unequal comparison for the purposes of sorting, where the endianness doesn't matter: fs/afs/addr_list.c:246:21: warning: restricted __be16 degrades to integer fs/afs/addr_list.c:246:30: warning: restricted __be16 degrades to integer fs/afs/addr_list.c:248:21: warning: restricted __be32 degrades to integer fs/afs/addr_list.c:248:49: warning: restricted __be32 degrades to integer fs/afs/addr_list.c:283:21: warning: restricted __be16 degrades to integer fs/afs/addr_list.c:283:30: warning: restricted __be16 degrades to integer (*) afs_set_cb_interest() is not actually used and can be removed. (*) afs_cell_gc_delay() should be provided with a sysctl. (*) afs_cell_destroy() needs to use rcu_access_pointer() to read cell->vl_addrs. (*) afs_init_fs_cursor() should be static. (*) struct afs_vnode::permit_cache needs to be marked __rcu. (*) afs_server_rcu() needs to use rcu_access_pointer(). (*) afs_destroy_server() should use rcu_access_pointer() on server->addresses as the server object is no longer accessible. (*) afs_find_server() casts __be16/__be32 values to int in order to directly compare them for the purpose of finding a match in a list, but is should also annotate the cast with __force to avoid checker warnings. (*) afs_check_permit() accesses vnode->permit_cache outside of the RCU readlock, though it doesn't then access the value; the extraneous access is deleted. False positives: (*) Conditional locking around the code in xdr_decode_AFSFetchStatus. This can be dealt with in a separate patch. fs/afs/fsclient.c:148:9: warning: context imbalance in 'xdr_decode_AFSFetchStatus' - different lock contexts for basic block (*) Incorrect handling of seq-retry lock context balance: fs/afs/inode.c:455:38: warning: context imbalance in 'afs_getattr' - different lock contexts for basic block fs/afs/server.c:52:17: warning: context imbalance in 'afs_find_server' - different lock contexts for basic block fs/afs/server.c:128:17: warning: context imbalance in 'afs_find_server_by_uuid' - different lock contexts for basic block Errors: (*) afs_lookup_cell_rcu() needs to break out of the seq-retry loop, not go round again if it successfully found the workstation cell. (*) Fix UUID decode in afs_deliver_cb_probe_uuid(). (*) afs_cache_permit() has a missing rcu_read_unlock() before one of the jumps to the someone_else_changed_it label. Move the unlock to after the label. (*) afs_vl_get_addrs_u() is using ntohl() rather than htonl() when encoding to XDR. (*) afs_deliver_yfsvl_get_endpoints() is using htonl() rather than ntohl() when decoding from XDR. Signed-off-by: David Howells

afs: Fix permit refcounting

2017-12-01T11:40:43+00:00

Fix four refcount bugs in afs_cache_permit(): (1) When checking the result of the kzalloc(), we can't just return, but must put 'permits'. (2) We shouldn't put permits immediately after hashing a new permit as we need to keep the pointer stable so that we can check to see if vnode->permit_cache has changed before we decide whether to assign to it. (3) 'permits' is being put twice. (4) We need to put either the replacement or the thing replaced after the assignment to vnode->permit_cache. Without this, lots of the following are seen: Kernel BUG at ffffffffa039857b [verbose debug info unavailable] ------------[ cut here ]------------ Kernel BUG at ffffffffa039858a [verbose debug info unavailable] ------------[ cut here ]------------ The addresses are in the .text..refcount section of the kafs.ko module. Following the relocation records for the __ex_table section shows one to be due to the decrement in afs_put_permits() and the other to be key_get() in afs_cache_permit(). Occasionally, the following is seen: refcount_t overflow at afs_cache_permit+0x57d/0x5c0 [kafs] in cc1[562], uid/euid: 0/0 WARNING: CPU: 0 PID: 562 at kernel/panic.c:657 refcount_error_report+0x9c/0xac ... Reported-by: Marc Dionne Signed-off-by: David Howells Tested-by: Marc Dionne

afs: Fix file locking

2017-11-17T10:06:13+00:00

Fix the AFS file locking whereby the use of the big kernel lock (which could be slept with) was replaced by a spinlock (which couldn't). The problem is that the AFS code was doing stuff inside the critical section that might call schedule(), so this is a broken transformation. Fix this by the following means: (1) Use a state machine with a proper state that can only be changed under the spinlock rather than using a collection of bit flags. (2) Cache the key used for the lock and the lock type in the afs_vnode struct so that the manager work function doesn't have to refer to a file_lock struct that's been dequeued. This makes signal handling safer. (4) Move the unlock from afs_do_unlk() to afs_fl_release_private() which means that unlock is achieved in other circumstances too. (5) Unlock the file on the server before taking the next conflicting lock. Also change: (1) Check the permits on a file before actually trying the lock. (2) fsync the file before effecting an explicit unlock operation. We don't fsync if the lock is erased otherwise as we might not be in a context where we can actually do that. Further fixes: (1) Fixed-fileserver address rotation is made to work. It's only used by the locking functions, so couldn't be tested before. Fixes: 72f98e72551f ("locks: turn lock_flocks into a spinlock") Signed-off-by: David Howells cc: jlayton@redhat.com

afs: Overhaul volume and server record caching and fileserver rotation

2017-11-13T15:38:19+00:00

The current code assumes that volumes and servers are per-cell and are never shared, but this is not enforced, and, indeed, public cells do exist that are aliases of each other. Further, an organisation can, say, set up a public cell and a private cell with overlapping, but not identical, sets of servers. The difference is purely in the database attached to the VL servers. The current code will malfunction if it sees a server in two cells as it assumes global address -> server record mappings and that each server is in just one cell. Further, each server may have multiple addresses - and may have addresses of different families (IPv4 and IPv6, say). To this end, the following structural changes are made: (1) Server record management is overhauled: (a) Server records are made independent of cell. The namespace keeps track of them, volume records have lists of them and each vnode has a server on which its callback interest currently resides. (b) The cell record no longer keeps a list of servers known to be in that cell. (c) The server records are now kept in a flat list because there's no single address to sort on. (d) Server records are now keyed by their UUID within the namespace. (e) The addresses for a server are obtained with the VL.GetAddrsU rather than with VL.GetEntryByName, using the server's UUID as a parameter. (f) Cached server records are garbage collected after a period of non-use and are counted out of existence before purging is allowed to complete. This protects the work functions against rmmod. (g) The servers list is now in /proc/fs/afs/servers. (2) Volume record management is overhauled: (a) An RCU-replaceable server list is introduced. This tracks both servers and their coresponding callback interests. (b) The superblock is now keyed on cell record and numeric volume ID. (c) The volume record is now tied to the superblock which mounts it, and is activated when mounted and deactivated when unmounted. This makes it easier to handle the cache cookie without causing a double-use in fscache. (d) The volume record is loaded from the VLDB using VL.GetEntryByNameU to get the server UUID list. (e) The volume name is updated if it is seen to have changed when the volume is updated (the update is keyed on the volume ID). (3) The vlocation record is got rid of and VLDB records are no longer cached. Sufficient information is stored in the volume record, though an update to a volume record is now no longer shared between related volumes (volumes come in bundles of three: R/W, R/O and backup). and the following procedural changes are made: (1) The fileserver cursor introduced previously is now fleshed out and used to iterate over fileservers and their addresses. (2) Volume status is checked during iteration, and the server list is replaced if a change is detected. (3) Server status is checked during iteration, and the address list is replaced if a change is detected. (4) The abort code is saved into the address list cursor and -ECONNABORTED returned in afs_make_call() if a remote abort happened rather than translating the abort into an error message. This allows actions to be taken depending on the abort code more easily. (a) If a VMOVED abort is seen then this is handled by rechecking the volume and restarting the iteration. (b) If a VBUSY, VRESTARTING or VSALVAGING abort is seen then this is handled by sleeping for a short period and retrying and/or trying other servers that might serve that volume. A message is also displayed once until the condition has cleared. (c) If a VOFFLINE abort is seen, then this is handled as VBUSY for the moment. (d) If a VNOVOL abort is seen, the volume is rechecked in the VLDB to see if it has been deleted; if not, the fileserver is probably indicating that the volume couldn't be attached and needs salvaging. (e) If statfs() sees one of these aborts, it does not sleep, but rather returns an error, so as not to block the umount program. (5) The fileserver iteration functions in vnode.c are now merged into their callers and more heavily macroised around the cursor. vnode.c is removed. (6) Operations on a particular vnode are serialised on that vnode because the server will lock that vnode whilst it operates on it, so a second op sent will just have to wait. (7) Fileservers are probed with FS.GetCapabilities before being used. This is where service upgrade will be done. (8) A callback interest on a fileserver is set up before an FS operation is performed and passed through to afs_make_call() so that it can be set on the vnode if the operation returns a callback. The callback interest is passed through to afs_iget() also so that it can be set there too. In general, record updating is done on an as-needed basis when we try to access servers, volumes or vnodes rather than offloading it to work items and special threads. Notes: (1) Pre AFS-3.4 servers are no longer supported, though this can be added back if necessary (AFS-3.4 was released in 1998). (2) VBUSY is retried forever for the moment at intervals of 1s. (3) /proc/fs/afs//servers no longer exists. Signed-off-by: David Howells

afs: Overhaul permit caching

2017-11-13T15:38:18+00:00

Overhaul permit caching in AFS by making it per-vnode and sharing permit lists where possible. When most of the fileserver operations are called, they return a status structure indicating the (revised) details of the vnode or vnodes involved in the operation. This includes the access mark derived from the ACL (named CallerAccess in the protocol definition file). This is cacheable and if the ACL changes, the server will tell us that it is breaking the callback promise, at which point we can discard the currently cached permits. With this patch, the afs_permits structure has, at the end, an array of { key, CallerAccess } elements, sorted by key pointer. This is then cached in a hash table so that it can be shared between vnodes with the same access permits. Permit lists can only be shared if they contain the exact same set of key->CallerAccess mappings. Note that that table is global rather than being per-net_ns. If the keys in a permit list cross net_ns boundaries, there is no problem sharing the cached permits, since the permits are just integer masks. Since permit lists pin keys, the permit cache also makes it easier for a future patch to find all occurrences of a key and remove them by means of setting the afs_permits::invalidated flag and then clearing the appropriate key pointer. In such an event, memory barriers will need adding. Lastly, the permit caching is skipped if the server has sent either a vnode-specific or an entire-server callback since the start of the operation. Signed-off-by: David Howells