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    Subject[094/262] nfsd4: permit read opens of executable-only files
    3.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "J. Bruce Fields" <bfields@redhat.com>

    commit a043226bc140a2c1dde162246d68a67e5043e6b2 upstream.

    A client that wants to execute a file must be able to read it. Read
    opens over nfs are therefore implicitly allowed for executable files
    even when those files are not readable.

    NFSv2/v3 get this right by using a passed-in NFSD_MAY_OWNER_OVERRIDE on
    read requests, but NFSv4 has gotten this wrong ever since
    dc730e173785e29b297aa605786c94adaffe2544 "nfsd4: fix owner-override on
    open", when we realized that the file owner shouldn't override
    permissions on non-reclaim NFSv4 opens.

    So we can't use NFSD_MAY_OWNER_OVERRIDE to tell nfsd_permission to allow
    reads of executable files.

    So, do the same thing we do whenever we encounter another weird NFS
    permission nit: define yet another NFSD_MAY_* flag.

    The industry's future standardization on 128-bit processors will be
    motivated primarily by the need for integers with enough bits for all
    the NFSD_MAY_* flags.

    Reported-by: Leonardo Borda <leonardoborda@gmail.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/nfsd/nfs4proc.c | 2 ++
    fs/nfsd/vfs.c | 3 ++-
    fs/nfsd/vfs.h | 1 +
    3 files changed, 5 insertions(+), 1 deletion(-)

    --- a/fs/nfsd/nfs4proc.c
    +++ b/fs/nfsd/nfs4proc.c
    @@ -156,6 +156,8 @@ do_open_permission(struct svc_rqst *rqst
    !(open->op_share_access & NFS4_SHARE_ACCESS_WRITE))
    return nfserr_inval;

    + accmode |= NFSD_MAY_READ_IF_EXEC;
    +
    if (open->op_share_access & NFS4_SHARE_ACCESS_READ)
    accmode |= NFSD_MAY_READ;
    if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE)
    --- a/fs/nfsd/vfs.c
    +++ b/fs/nfsd/vfs.c
    @@ -2114,7 +2114,8 @@ nfsd_permission(struct svc_rqst *rqstp,

    /* Allow read access to binaries even when mode 111 */
    if (err == -EACCES && S_ISREG(inode->i_mode) &&
    - acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE))
    + (acc == (NFSD_MAY_READ | NFSD_MAY_OWNER_OVERRIDE) ||
    + acc == (NFSD_MAY_READ | NFSD_MAY_READ_IF_EXEC)))
    err = inode_permission(inode, MAY_EXEC);

    return err? nfserrno(err) : 0;
    --- a/fs/nfsd/vfs.h
    +++ b/fs/nfsd/vfs.h
    @@ -25,6 +25,7 @@
    #define NFSD_MAY_BYPASS_GSS_ON_ROOT 256
    #define NFSD_MAY_NOT_BREAK_LEASE 512
    #define NFSD_MAY_BYPASS_GSS 1024
    +#define NFSD_MAY_READ_IF_EXEC 2048

    #define NFSD_MAY_CREATE (NFSD_MAY_EXEC|NFSD_MAY_WRITE)
    #define NFSD_MAY_REMOVE (NFSD_MAY_EXEC|NFSD_MAY_WRITE|NFSD_MAY_TRUNC)



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