[PATCH 0/3] afs: Miscellaneous fixes

[PATCH 0/3] afs: Miscellaneous fixes

[David Howells]

Hi Christian,

Can you pick up these miscellaneous AFS fixes, please?  Note that most of
these are derived from Sashiko review of some rxrpc patches[1][2].

 (1) Fix afs_fs_fetch_data() to set call->async.

 (2) Fix afs_fs_fetch_data() to subtract transferred from len instead of
     adding it.

 (3) Fix a UAF when sending a message if the call is completed so quickly
     that the sending code hasn't finished with it when it gets freed.

The patches can be found here:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-fixes

Thanks,
David

[1] https://sashiko.dev/#/patchset/20260702144919.172295-1-dhowells%40redh
[2] https://sashiko.dev/#/patchset/20260713081022.2186481-1-dhowells%40red

David Howells (3):
  afs: Fix afs_fs_fetch_data() to set call->async
  afs: Fix afs_fs_fetch_data() to subtract transferred from len
  afs: Fix UAF when sending a message

 fs/afs/fsclient.c | 5 ++++-
 fs/afs/internal.h | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

[PATCH 1/3] afs: Fix afs_fs_fetch_data() to set call->async

[David Howells]

Fix afs_fs_fetch_data() to set call->async on an async operation as does
afs_fs_fetch_data64().

Fixes: eddf51f2bb2c ("afs: Make {Y,}FS.FetchData an asynchronous operation")
Link: https://sashiko.dev/#/patchset/20260702144919.172295-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
---
 fs/afs/fsclient.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index a2ffd60889f8..626e1d37b915 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -477,6 +477,9 @@ void afs_fs_fetch_data(struct afs_operation *op)
 	if (!call)
 		return afs_op_nomem(op);
 
+	if (op->flags & AFS_OPERATION_ASYNC)
+		call->async = true;
+
 	/* marshall the parameters */
 	bp = call->request;
 	bp[0] = htonl(FSFETCHDATA);

[PATCH 2/3] afs: Fix afs_fs_fetch_data() to subtract transferred from len

[David Howells]

Fix afs_fs_fetch_data() to subtract subreq->transferred from subreq->len
rather than adding it.

Fixes: f28fc2010d62 ("afs: Eliminate afs_read")
Link: https://sashiko.dev/#/patchset/20260713081022.2186481-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
---
 fs/afs/fsclient.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 626e1d37b915..1a3f186a6a11 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -487,7 +487,7 @@ void afs_fs_fetch_data(struct afs_operation *op)
 	bp[2] = htonl(vp->fid.vnode);
 	bp[3] = htonl(vp->fid.unique);
 	bp[4] = htonl(lower_32_bits(subreq->start + subreq->transferred));
-	bp[5] = htonl(lower_32_bits(subreq->len   + subreq->transferred));
+	bp[5] = htonl(lower_32_bits(subreq->len   - subreq->transferred));
 
 	call->fid = vp->fid;
 	trace_afs_make_fs_call(call, &vp->fid);

[PATCH 3/3] afs: Fix UAF when sending a message

[David Howells]

In afs_make_call(), there's a race with async call reception and
destruction.  If a call is dispatched that doesn't have call->write_iter
set (used to specify the data content for FS.StoreData), then the first
rxrpc_kernel_send_data() will not set MSG_MORE in the msghdr.

Once rxrpc_send_data() queues the last request packet, the response could
come in at any time and cause the call to be completed and put.  However,
afs_make_call() will look at the call again to see it ->write_iter should
be handled - something it's only allowed to do if it has its own ref on the
call.  Whilst this is the case for synchronous calls, it isn't true for
async calls such as FS.FetchData.

There's also a potential UAF in afs_make_call() in the event that an
asynchronous call is being sent, but the call fails in some way (e.g. it
gets aborted from the server).  The problem there is that afs_make_call()
tries to abort a call if the rxrpc send fails, but the asynchronous
notification from rxrpc may have caused the afs_call to be torn down.

generic/650 plays games with randomly taking CPUs offline, and can
interject a significant delay such that the call is deallocated before
afs_make_call() gets to check call->write_iter - and a UAF ensues (caught
by KASAN).

   BUG: KASAN: slab-use-after-free in afs_make_call+0x1c90/0x2210 [kafs]
   Read of size 8 at addr ffff888035e050e8 by task fsstress/1409

Fix this by making afs_make_op_call() give the op->call its own ref rather
than transferring the caller's ref to it and then dropping the ref when
afs_make_call() returns.

This also means that the afs_make_call() func never loses its ref on the
call now.

Fixes: eddf51f2bb2c ("afs: Make {Y,}FS.FetchData an asynchronous operation")
Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept")
Link: https://sashiko.dev/#/patchset/20260702144919.172295-1-dhowells%40redhat.com
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
---
 fs/afs/internal.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 601f01e5c15f..290873bac89b 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -1421,7 +1421,7 @@ static inline void afs_make_op_call(struct afs_operation *op, struct afs_call *c
 {
 	struct afs_addr_list *alist = op->estate->addresses;
 
-	op->call	= call;
+	op->call	= afs_get_call(call, afs_call_trace_get);
 	op->type	= call->type;
 	call->op	= op;
 	call->key	= op->key;
@@ -1429,6 +1429,7 @@ static inline void afs_make_op_call(struct afs_operation *op, struct afs_call *c
 	call->peer	= rxrpc_kernel_get_peer(alist->addrs[op->addr_index].peer);
 	call->service_id = op->server->service_id;
 	afs_make_call(call, gfp);
+	afs_put_call(call);
 }
 
 static inline void afs_extract_begin(struct afs_call *call, void *buf, size_t size)