z3fold: fix use-after-free when freeing handles
free_handle() for a foreign handle may race with inter-page compaction,
what can lead to memory corruption.
To avoid that, take write lock not read lock in free_handle to be
synchronized with __release_z3fold_page().
For example KASAN can detect it:
==================================================================
BUG: KASAN: use-after-free in LZ4_decompress_safe+0x2c4/0x3b8
Read of size 1 at addr ffffffc976695ca3 by task GoogleApiHandle/4121
CPU: 0 PID: 4121 Comm: GoogleApiHandle Tainted: P S OE 4.19.81-perf+ #162
Hardware name: Sony Mobile Communications. PDX-203(KONA) (DT)
Call trace:
LZ4_decompress_safe+0x2c4/0x3b8
lz4_decompress_crypto+0x3c/0x70
crypto_decompress+0x58/0x70
zcomp_decompress+0xd4/0x120
...
Apart from that, initialize zhdr->mapped_count in init_z3fold_page() and
remove "newpage" variable because it is not used anywhere.
Signed-off-by: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Raymond Jennings <shentino@gmail.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200520082100.28876-1-vitaly.wool@konsulko.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 file changed