[PATCH 4.14 17/25] regmap: Fix possible double-free in regcache_rbtree_exit()

Greg Kroah-Hartman
2021-11-01T09:22:39Z

From: Yang Yingliang <yangyingliang@huawei.com>

commit 55e6d8037805b3400096d621091dfbf713f97e83 upstream.

In regcache_rbtree_insert_to_block(), when 'present' realloc failed,
the 'blk' which is supposed to assign to 'rbnode->block' will be freed,
so 'rbnode->block' points a freed memory, in the error handling path of
regcache_rbtree_init(), 'rbnode->block' will be freed again in
regcache_rbtree_exit(), KASAN will report double-free as follows:

BUG: KASAN: double-free or invalid-free in kfree+0xce/0x390
Call Trace:
slab_free_freelist_hook+0x10d/0x240
kfree+0xce/0x390
regcache_rbtree_exit+0x15d/0x1a0
regcache_rbtree_init+0x224/0x2c0
regcache_init+0x88d/0x1310
__regmap_init+0x3151/0x4a80
__devm_regmap_init+0x7d/0x100
madera_spi_probe+0x10f/0x333 [madera_spi]
spi_probe+0x183/0x210
really_probe+0x285/0xc30

To fix this, moving up the assignment of rbnode->block to immediately after
the reallocation has succeeded so that the data structure stays valid even
if the second reallocation fails.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 3f4ff561bc88b ("regmap: rbtree: Make cache_present bitmap per node")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20211012023735.1632786-1-yangyingliang@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/base/regmap/regcache-rbtree.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/base/regmap/regcache-rbtree.c
+++ b/drivers/base/regmap/regcache-rbtree.c
@@ -295,14 +295,14 @@ static int regcache_rbtree_insert_to_blo
if (!blk)
return -ENOMEM;

+ rbnode->block = blk;
+
if (BITS_TO_LONGS(blklen) > BITS_TO_LONGS(rbnode->blklen)) {
present = krealloc(rbnode->cache_present,
BITS_TO_LONGS(blklen) * sizeof(*present),
GFP_KERNEL);
- if (!present) {
- kfree(blk);
+ if (!present)
return -ENOMEM;
- }

memset(present + BITS_TO_LONGS(rbnode->blklen), 0,
(BITS_TO_LONGS(blklen) - BITS_TO_LONGS(rbnode->blklen))
@@ -319,7 +319,6 @@ static int regcache_rbtree_insert_to_blo
}

/* update the rbnode block, its size and the base register */
- rbnode->block = blk;
rbnode->blklen = blklen;
rbnode->base_reg = base_reg;
rbnode->cache_present = present;