Amazon EFS provides an NFSv4.1 filesystem which appears to use (close to) full length (128 byte) file handles. This causes the handle reported by name_to_handle_at() to exceed MAX_HANDLE_SZ, resulting in EOVERFLOW if 128 bytes were requested, or EINVAL if the size reported by the previous call was requested. To fix this, increase MAX_HANDLE_SIZE a little, and add a BUILD_BUG so that this sort of inconsistent error reporting won't happen again. Link: https://github.com/systemd/systemd/issues/7082#issuecomment-347380436 Signed-off-by: NeilBrown <neilb@xxxxxxxx> --- Sorry for the scatter-gun To: list. This is really more of a VFS patch than an NFS patch and sending patches in either direction has been a bit hit-and-miss lately, so I'm hoping Andrew will take it unless someone else objects or beats him to it... Thanks, NeilBrown fs/nfs/export.c | 2 ++ include/linux/exportfs.h | 7 +++++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/nfs/export.c b/fs/nfs/export.c index 83fd09fc8f77..23b2fc3ab2bb 100644 --- a/fs/nfs/export.c +++ b/fs/nfs/export.c @@ -39,6 +39,8 @@ nfs_encode_fh(struct inode *inode, __u32 *p, int *max_len, struct inode *parent) size_t fh_size = offsetof(struct nfs_fh, data) + server_fh->size; int len = EMBED_FH_OFF + XDR_QUADLEN(fh_size); + BUILD_BUG_ON_MSG(EMBED_FH_OFF + NFS_MAXFHSIZE > MAX_HANDLE_SZ, + "MAX_HANDLE_SZ is too small"); dprintk("%s: max fh len %d inode %p parent %p", __func__, *max_len, inode, parent); diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h index 0d3037419bc7..e7ab1b071c5e 100644 --- a/include/linux/exportfs.h +++ b/include/linux/exportfs.h @@ -11,8 +11,11 @@ struct iomap; struct super_block; struct vfsmount; -/* limit the handle size to NFSv4 handle size now */ -#define MAX_HANDLE_SZ 128 +/* Must be larger than NFSv4 file handle, but small + * enough for an on-stack allocation. overlayfs doesn't + * want this too close to 255. + */ +#define MAX_HANDLE_SZ 200 /* * The fileid_type identifies how the file within the filesystem is encoded. -- 2.14.0.rc0.dirty
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