This is a note to let you know that I've just added the patch titled regmap: Fix possible double-free in regcache_rbtree_exit() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: regmap-fix-possible-double-free-in-regcache_rbtree_exit.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 55e6d8037805b3400096d621091dfbf713f97e83 Mon Sep 17 00:00:00 2001 From: Yang Yingliang <yangyingliang@xxxxxxxxxx> Date: Tue, 12 Oct 2021 10:37:35 +0800 Subject: regmap: Fix possible double-free in regcache_rbtree_exit() From: Yang Yingliang <yangyingliang@xxxxxxxxxx> 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@xxxxxxxxxx> Fixes: 3f4ff561bc88b ("regmap: rbtree: Make cache_present bitmap per node") Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx> Link: https://lore.kernel.org/r/20211012023735.1632786-1-yangyingliang@xxxxxxxxxx Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -296,14 +296,14 @@ 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)) @@ -320,7 +320,6 @@ 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; Patches currently in stable-queue which might be from yangyingliang@xxxxxxxxxx are queue-4.4/regmap-fix-possible-double-free-in-regcache_rbtree_exit.patch