staging: lustre: simplify capability dropping.

Lustre has a 'squash credentials' concept similar to the "anon_uid"
for nfsd.  When accessing a file with squashed credentials, we
need to also drop capabilities.
Linux has cap_drop_fs_set() and cap_drop_nfsd_set().  Rather than
taking a completely different approach, this patch changes lustre
to use this same cap_drop_*_set() approach.

With this change we also drop CAP_MKNOD and CAP_MAC_OVERRIDE
which are probably appropriate, and don't drop
CAP_SYS_ADMIN or CAP_SYS_BOOT which should be irrelevant for
file permission checking

Calling both cap_drop_*_set() seems a bit clumsy, but gets
the job done.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/lustre/include/linux/libcfs/curproc.h b/drivers/staging/lustre/include/linux/libcfs/curproc.h
index 83526f8..fc6f6eb 100644 (file)
--- a/drivers/staging/lustre/include/linux/libcfs/curproc.h
+++ b/drivers/staging/lustre/include/linux/libcfs/curproc.h
@@ -50,16 +50,6 @@
 
 typedef u32 cfs_cap_t;
 
-#define CFS_CAP_FS_MASK (BIT(CAP_CHOWN) |              \
-                        BIT(CAP_DAC_OVERRIDE) |        \
-                        BIT(CAP_DAC_READ_SEARCH) |     \
-                        BIT(CAP_FOWNER) |              \
-                        BIT(CAP_FSETID) |              \
-                        BIT(CAP_LINUX_IMMUTABLE) | \
-                        BIT(CAP_SYS_ADMIN) |   \
-                        BIT(CAP_SYS_BOOT) |    \
-                        BIT(CAP_SYS_RESOURCE))
-
 static inline cfs_cap_t cfs_curproc_cap_pack(void)
 {
        /* cfs_cap_t is only the first word of kernel_cap_t */

diff --git a/drivers/staging/lustre/lustre/llite/file.c b/drivers/staging/lustre/lustre/llite/file.c
index 0026fde..a77cadc 100644 (file)
--- a/drivers/staging/lustre/lustre/llite/file.c
+++ b/drivers/staging/lustre/lustre/llite/file.c
@@ -3050,7 +3050,6 @@ int ll_inode_permission(struct inode *inode, int mask)
        const struct cred *old_cred = NULL;
        struct cred *cred = NULL;
        bool squash_id = false;
-       cfs_cap_t cap;
        int rc = 0;
 
        if (mask & MAY_NOT_BLOCK)
@@ -3094,10 +3093,9 @@ int ll_inode_permission(struct inode *inode, int mask)
 
                cred->fsuid = make_kuid(&init_user_ns, squash->rsi_uid);
                cred->fsgid = make_kgid(&init_user_ns, squash->rsi_gid);
-               for (cap = 0; cap < sizeof(cfs_cap_t) * 8; cap++) {
-                       if ((1 << cap) & CFS_CAP_FS_MASK)
-                               cap_lower(cred->cap_effective, cap);
-               }
+               cred->cap_effective = cap_drop_nfsd_set(cred->cap_effective);
+               cred->cap_effective = cap_drop_fs_set(cred->cap_effective);
+
                old_cred = override_creds(cred);
        }