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

From: Jiri Slaby
Date: Tue Nov 18 2014 - 10:15:45 EST

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) {

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