From: David Howells dhowells@redhat.com
commit 64fcbb6158ecc684d84c64424830a9c37c77c5b9 upstream.
If someone attempts to access YFS-related xattrs (e.g. afs.yfs.acl) on a file on a non-YFS AFS server (such as OpenAFS), then the kernel will jump to a NULL function pointer because the afs_fetch_acl_operation descriptor doesn't point to a function for issuing an operation on a non-YFS server[1].
Fix this by making afs_wait_for_operation() check that the issue_afs_rpc method is set before jumping to it and setting -ENOTSUPP if not. This fix also covers other potential operations that also only exist on YFS servers.
afs_xattr_get/set_yfs() then need to translate -ENOTSUPP to -ENODATA as the former error is internal to the kernel.
The bug shows up as an oops like the following:
BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. [...] Call Trace: afs_wait_for_operation+0x83/0x1b0 [kafs] afs_xattr_get_yfs+0xe6/0x270 [kafs] __vfs_getxattr+0x59/0x80 vfs_getxattr+0x11c/0x140 getxattr+0x181/0x250 ? __check_object_size+0x13f/0x150 ? __fput+0x16d/0x250 __x64_sys_fgetxattr+0x64/0xb0 do_syscall_64+0x49/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fb120a9defe
This was triggered with "cp -a" which attempts to copy xattrs, including afs ones, but is easier to reproduce with getfattr, e.g.:
getfattr -d -m ".*" /afs/openafs.org/
Fixes: e49c7b2f6de7 ("afs: Build an abstraction around an "operation" concept") Reported-by: Gaja Sophie Peters gaja.peters@math.uni-hamburg.de Signed-off-by: David Howells dhowells@redhat.com Tested-by: Gaja Sophie Peters gaja.peters@math.uni-hamburg.de Reviewed-by: Marc Dionne marc.dionne@auristor.com Reviewed-by: Jeffrey Altman jaltman@auristor.com cc: linux-afs@lists.infradead.org Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003498.html [1] Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003566.html # v1 Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003572.html # v2 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/afs/fs_operation.c | 7 +++++-- fs/afs/xattr.c | 8 +++++++- 2 files changed, 12 insertions(+), 3 deletions(-)
--- a/fs/afs/fs_operation.c +++ b/fs/afs/fs_operation.c @@ -181,10 +181,13 @@ void afs_wait_for_operation(struct afs_o if (test_bit(AFS_SERVER_FL_IS_YFS, &op->server->flags) && op->ops->issue_yfs_rpc) op->ops->issue_yfs_rpc(op); - else + else if (op->ops->issue_afs_rpc) op->ops->issue_afs_rpc(op); + else + op->ac.error = -ENOTSUPP;
- op->error = afs_wait_for_call_to_complete(op->call, &op->ac); + if (op->call) + op->error = afs_wait_for_call_to_complete(op->call, &op->ac); }
switch (op->error) { --- a/fs/afs/xattr.c +++ b/fs/afs/xattr.c @@ -230,6 +230,8 @@ static int afs_xattr_get_yfs(const struc else ret = -ERANGE; } + } else if (ret == -ENOTSUPP) { + ret = -ENODATA; }
error_yacl: @@ -254,6 +256,7 @@ static int afs_xattr_set_yfs(const struc { struct afs_operation *op; struct afs_vnode *vnode = AFS_FS_I(inode); + int ret;
if (flags == XATTR_CREATE || strcmp(name, "acl") != 0) @@ -268,7 +271,10 @@ static int afs_xattr_set_yfs(const struc return afs_put_operation(op);
op->ops = &yfs_store_opaque_acl2_operation; - return afs_do_sync_operation(op); + ret = afs_do_sync_operation(op); + if (ret == -ENOTSUPP) + ret = -ENODATA; + return ret; }
static const struct xattr_handler afs_xattr_yfs_handler = {