On Tue, Oct 11, 2022 at 10:25:16AM -0500, Gustavo A. R. Silva wrote: > On Mon, Oct 10, 2022 at 11:52:43PM -0700, Kees Cook wrote: > > The 'nfs_server' and 'mount_server' structures include a union of > > 'struct sockaddr' (with the older 16 bytes max address size) and > > 'struct sockaddr_storage' which is large enough to hold all the supported > > sa_family types (128 bytes max size). The runtime memcpy() buffer overflow > > checker is seeing attempts to write beyond the 16 bytes as an overflow, > > but the actual expected size is that of 'struct sockaddr_storage'. Adjust > > the pointers to the correct union member. Avoids this false positive > > run-time warning under CONFIG_FORTIFY_SOURCE: > > > > memcpy: detected field-spanning write (size 28) of single field "&ctx->nfs_server.address" at fs/nfs/namespace.c:178 (size 16) > > > > Reported-by: kernel test robot <yujie.liu@xxxxxxxxx> > > Link: https://lore.kernel.org/all/202210110948.26b43120-yujie.liu@xxxxxxxxx > > Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > > Cc: Anna Schumaker <anna@xxxxxxxxxx> > > Cc: linux-nfs@xxxxxxxxxxxxxxx > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> Thanks! > > --- > > fs/nfs/fs_context.c | 2 +- > > fs/nfs/namespace.c | 2 +- > > fs/nfs/super.c | 4 ++-- > > 3 files changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c > > index 4da701fd1424..bffa31bb35b9 100644 > > --- a/fs/nfs/fs_context.c > > +++ b/fs/nfs/fs_context.c > > @@ -1540,7 +1540,7 @@ static int nfs_init_fs_context(struct fs_context *fc) > > ctx->version = nfss->nfs_client->rpc_ops->version; > > ctx->minorversion = nfss->nfs_client->cl_minorversion; > > > > - memcpy(&ctx->nfs_server.address, &nfss->nfs_client->cl_addr, > > + memcpy(&ctx->nfs_server._address, &nfss->nfs_client->cl_addr, > > ctx->nfs_server.addrlen); So, I spent a bunch more time looking at the plumbing of struct sockaddr vs struct sockaddr_storage. In NFS, everything I could find is actually already backed by a full sockaddr_storage, so I think a more complete fix here would actually be to update all the internals to pass sockaddr_storage instead of sockaddr. The interfaces to other things (e.g. rpc) can cast back to sockaddr for now. It is a pretty reasonable cleanup, IMO. I'll send a follow-up that makes this change on top of this patch, though they could be squashed if that was desired. -- Kees Cook
