• Jeff Layton's avatar
    RPC: add wrapper for svc_reserve to account for checksum · cd123012
    Jeff Layton authored
    When the kernel calls svc_reserve to downsize the expected size of an RPC
    reply, it fails to account for the possibility of a checksum at the end of
    the packet.  If a client mounts a NFSv2/3 with sec=krb5i/p, and does I/O
    then you'll generally see messages similar to this in the server's ring
    buffer:
    
    RPC request reserved 164 but used 208
    
    While I was never able to verify it, I suspect that this problem is also
    the root cause of some oopses I've seen under these conditions:
    
    https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=227726
    
    This is probably also a problem for other sec= types and for NFSv4.  The
    large reserved size for NFSv4 compound packets seems to generally paper
    over the problem, however.
    
    This patch adds a wrapper for svc_reserve that accounts for the possibility
    of a checksum.  It also fixes up the appropriate callers of svc_reserve to
    call the wrapper.  For now, it just uses a hardcoded value that I
    determined via testing.  That value may need to be revised upward as things
    change, or we may want to eventually add a new auth_op that attempts to
    calculate this somehow.
    
    Unfortunately, there doesn't seem to be a good way to reliably determine
    the expected checksum length prior to actually calculating it, particularly
    with schemes like spkm3.
    Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
    Acked-by: default avatarNeil Brown <neilb@suse.de>
    Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
    Acked-by: default avatarJ. Bruce Fields <bfields@citi.umich.edu>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    cd123012
nfs3proc.c 18 KB