remove lots of IS_ERR_VALUE abuses

Most users of IS_ERR_VALUE() in the kernel are wrong, as they
pass an 'int' into a function that takes an 'unsigned long'
argument. This happens to work because the type is sign-extended
on 64-bit architectures before it gets converted into an
unsigned type.

However, anything that passes an 'unsigned short' or 'unsigned int'
argument into IS_ERR_VALUE() is guaranteed to be broken, as are
8-bit integers and types that are wider than 'unsigned long'.

Andrzej Hajda has already fixed a lot of the worst abusers that
were causing actual bugs, but it would be nice to prevent any
users that are not passing 'unsigned long' arguments.

This patch changes all users of IS_ERR_VALUE() that I could find
on 32-bit ARM randconfig builds and x86 allmodconfig. For the
moment, this doesn't change the definition of IS_ERR_VALUE()
because there are probably still architecture specific users
elsewhere.

Almost all the warnings I got are for files that are better off
using 'if (err)' or 'if (err < 0)'.
The only legitimate user I could find that we get a warning for
is the (32-bit only) freescale fman driver, so I did not remove
the IS_ERR_VALUE() there but changed the type to 'unsigned long'.
For 9pfs, I just worked around one user whose calling conventions
are so obscure that I did not dare change the behavior.

I was using this definition for testing:

 #define IS_ERR_VALUE(x) ((unsigned long*)NULL == (typeof (x)*)NULL && \
       unlikely((unsigned long long)(x) >= (unsigned long long)(typeof(x))-MAX_ERRNO))

which ends up making all 16-bit or wider types work correctly with
the most plausible interpretation of what IS_ERR_VALUE() was supposed
to return according to its users, but also causes a compile-time
warning for any users that do not pass an 'unsigned long' argument.

I suggested this approach earlier this year, but back then we ended
up deciding to just fix the users that are obviously broken. After
the initial warning that caused me to get involved in the discussion
(fs/gfs2/dir.c) showed up again in the mainline kernel, Linus
asked me to send the whole thing again.

[ Updated the 9p parts as per Al Viro  - Linus ]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.org/lkml/2016/1/7/363
Link: https://lkml.org/lkml/2016/5/27/486
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> # For nvmem part
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 12 insertions, 13 deletions

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 65de439bdc4f..14d506efd1aa 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -643,10 +643,6 @@ ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from)
 		return 0;
 
 	result = generic_file_write_iter(iocb, from);
-	if (IS_ERR_VALUE(result)) {
-		_leave(" = %zd", result);
-		return result;
-	}
 
 	_leave(" = %zd", result);
 	return result;
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index f723cd3a455c..caf9e39bb82b 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -337,7 +337,7 @@ calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
 					"(%d != %d)", (unsigned) r, curid, id);
 			goto failed;
 		} else if ( ! p->lib_list[id].loaded &&
-				IS_ERR_VALUE(load_flat_shared_library(id, p))) {
+				load_flat_shared_library(id, p) < 0) {
 			printk("BINFMT_FLAT: failed to load library %d", id);
 			goto failed;
 		}
@@ -837,7 +837,7 @@ static int load_flat_shared_library(int id, struct lib_info *libs)
 
 	res = prepare_binprm(&bprm);
 
-	if (!IS_ERR_VALUE(res))
+	if (!res)
 		res = load_flat_file(&bprm, libs, id, NULL);
 
 	abort_creds(bprm.cred);
@@ -883,7 +883,7 @@ static int load_flat_binary(struct linux_binprm * bprm)
 	stack_len += FLAT_STACK_ALIGN - 1;  /* reserve for upcoming alignment */
 	
 	res = load_flat_file(bprm, &libinfo, 0, &stack_len);
-	if (IS_ERR_VALUE(res))
+	if (res < 0)
 		return res;
 	
 	/* Update data segment pointers for all libraries */
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 4a01f30e9995..271d93905bac 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -783,12 +783,15 @@ static int get_leaf_nr(struct gfs2_inode *dip, u32 index,
 		       u64 *leaf_out)
 {
 	__be64 *hash;
+	int error;
 
 	hash = gfs2_dir_get_hash_table(dip);
-	if (IS_ERR(hash))
-		return PTR_ERR(hash);
-	*leaf_out = be64_to_cpu(*(hash + index));
-	return 0;
+	error = PTR_ERR_OR_ZERO(hash);
+
+	if (!error)
+		*leaf_out = be64_to_cpu(*(hash + index));
+
+	return error;
 }
 
 static int get_first_leaf(struct gfs2_inode *dip, u32 index,
@@ -798,7 +801,7 @@ static int get_first_leaf(struct gfs2_inode *dip, u32 index,
 	int error;
 
 	error = get_leaf_nr(dip, index, &leaf_no);
-	if (!IS_ERR_VALUE(error))
+	if (!error)
 		error = get_leaf(dip, leaf_no, bh_out);
 
 	return error;
@@ -1014,7 +1017,7 @@ static int dir_split_leaf(struct inode *inode, const struct qstr *name)
 
 	index = name->hash >> (32 - dip->i_depth);
 	error = get_leaf_nr(dip, index, &leaf_no);
-	if (IS_ERR_VALUE(error))
+	if (error)
 		return error;
 
 	/*  Get the old leaf block  */