fs: Preserve error code in get_empty_filp(), part 2

Allocating a file structure in function get_empty_filp() might fail because
of several reasons:
 - not enough memory for file structures
 - operation is not allowed
 - user is over its limit

Currently the function returns NULL in all cases and we loose the exact
reason of the error. All callers of get_empty_filp() assume that the function
can fail with ENFILE only.

Return error through pointer. Change all callers to preserve this error code.

[AV: cleaned up a bit, carved the get_empty_filp() part out into a separate commit
(things remaining here deal with alloc_file()), removed pipe(2) behaviour change]

Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 2 insertions, 1 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index 8c9402d..de389e6 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1042,7 +1042,8 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 			  is_file_hugepages(shp->shm_file) ?
 				&shm_file_operations_huge :
 				&shm_file_operations);
-	if (!file)
+	err = PTR_ERR(file);
+	if (IS_ERR(file))
 		goto out_free;
 
 	file->private_data = sfd;