afs: Fix possible oops in afs_lookup trace event
The afs_lookup trace event can cause the following:
[ 216.576777] BUG: kernel NULL pointer dereference, address: 000000000000023b
[ 216.576803] #PF: supervisor read access in kernel mode
[ 216.576813] #PF: error_code(0x0000) - not-present page
...
[ 216.576913] RIP: 0010:trace_event_raw_event_afs_lookup+0x9e/0x1c0 [kafs]
If the inode from afs_do_lookup() is an error other than ENOENT, or if it
is ENOENT and afs_try_auto_mntpt() returns an error, the trace event will
try to dereference the error pointer as a valid pointer.
Use IS_ERR_OR_NULL to only pass a valid pointer for the trace, or NULL.
Ideally the trace would include the error value, but for now just avoid
the oops.
Fixes: 80548b03991f ("afs: Add more tracepoints")
Signed-off-by: Marc Dionne <marc.dionne at auristor.com>
Signed-off-by: David Howells <dhowells at redhat.com>
UnifiedSplitRaw
