[PATCH 3.14 098/122] regmap: fix kernel hang on regmap_bulk_write with zero val_count.

[Greg Kroah-Hartman]

3.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>

Fixes commit 2f06fa04cf35da5c24481da3ac84a2900d0b99c3 which was an
incorrect backported version of commit
d6b41cb06044a7d895db82bdd54f6e4219970510 upstream.

If val_count is zero we return -EINVAL with map->lock_arg locked, which
will deadlock the kernel next time we try to acquire this lock.

This was introduced by f5942dd ("regmap: fix possible ZERO_SIZE_PTR pointer
dereferencing error.") which improperly back-ported d6b41cb0.

This issue was found during review of Ubuntu Trusty 3.13.0-40.68 kernel to
prepare Ksplice rebootless updates.

Fixes: f5942dd ("regmap: fix possible ZERO_SIZE_PTR pointer dereferencing error.")
Signed-off-by: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/base/regmap/regmap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1557,8 +1557,10 @@ int regmap_bulk_write(struct regmap *map
 	} else {
 		void *wval;
 
-		if (!val_count)
-			return -EINVAL;
+		if (!val_count) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		wval = kmemdup(val, val_count * val_bytes, GFP_KERNEL);
 		if (!wval) {


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