[PATCH 3.12 051/206] regmap: fix kernel hang on regmap_bulk_write with zero val_count.

[Jiri Slaby]

From: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>

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

===============

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.

In 3.12, this was introduced by a0b8d8d906d267987d507138003048c5fdf774
("regmap: fix possible ZERO_SIZE_PTR pointer dereferencing error.")
which improperly back-ported d6b41cb06044a7d895db82bdd54f6e4219970510.

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: Jiri Slaby <jslaby@xxxxxxx>
---
 drivers/base/regmap/regmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 7a58be457eb5..9f7990187653 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1403,8 +1403,10 @@ int regmap_bulk_write(struct regmap *map, unsigned int reg, const void *val,
 	if (val_bytes == 1) {
 		wval = (void *)val;
 	} else {
-		if (!val_count)
-			return -EINVAL;
+		if (!val_count) {
+			ret = -EINVAL;
+			goto out;
+		}
 
 		wval = kmemdup(val, val_count * val_bytes, GFP_KERNEL);
 		if (!wval) {
-- 
2.1.3

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