vfs_gpfs: Retry getacl with DAC capability if necessary

Samba always tries to read the ACL of a file and checks it internally.
If the READ_ACL permission is missing in GPFS, then then reading the ACL
for Samba internal evaluation will be denied and opening the file or
directory fails. Change this by retrying reading the ACL with the DAC
capability if access was denied.

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Christof Schmitt <cs@samba.org>
Autobuild-Date(master): Mon Jul 25 10:30:02 CEST 2016 on sn-devel-144

diff --git a/source3/modules/vfs_gpfs.c b/source3/modules/vfs_gpfs.c
index 42a3c720599ffa49bb0348a20dd7f38a525b60be..f096dd54abfbac2b8ca5cffcdba67852adf0871a 100644 (file)
--- a/source3/modules/vfs_gpfs.c
+++ b/source3/modules/vfs_gpfs.c
@@ -358,6 +358,21 @@ static void gpfs_dumpacl(int level, struct gpfs_acl *gacl)
        }
 }
 
+static int gpfs_getacl_with_capability(const char *fname, int flags, void *buf)
+{
+       int ret, saved_errno;
+
+       set_effective_capability(DAC_OVERRIDE_CAPABILITY);
+
+       ret = gpfswrap_getacl(discard_const_p(char, fname), flags, buf);
+       saved_errno = errno;
+
+       drop_effective_capability(DAC_OVERRIDE_CAPABILITY);
+
+       errno = saved_errno;
+       return ret;
+}
+
 /*
  * get the ACL from GPFS, allocated on the specified mem_ctx
  * internally retries when initial buffer was too small
@@ -378,6 +393,7 @@ static void *vfs_gpfs_getacl(TALLOC_CTX *mem_ctx,
        int ret, flags;
        unsigned int *len;
        size_t struct_size;
+       bool use_capability = false;
 
 again:
 
@@ -406,8 +422,18 @@ again:
        /* set the length of the buffer as input value */
        *len = size;
 
-       errno = 0;
-       ret = gpfswrap_getacl(discard_const_p(char, fname), flags, aclbuf);
+       if (use_capability) {
+               ret = gpfs_getacl_with_capability(fname, flags, aclbuf);
+       } else {
+               ret = gpfswrap_getacl(discard_const_p(char, fname),
+                                     flags, aclbuf);
+               if ((ret != 0) && (errno == EACCES)) {
+                       DBG_DEBUG("Retry with DAC capability for %s\n", fname);
+                       use_capability = true;
+                       ret = gpfs_getacl_with_capability(fname, flags, aclbuf);
+               }
+       }
+
        if ((ret != 0) && (errno == ENOSPC)) {
                /*
                 * get the size needed to accommodate the complete buffer