diff options
| author | Uladzislau Rezki | 2020-05-22 22:23:12 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2020-05-23 10:26:32 -0700 |
| commit | d8f117abb380ba968b5e3ef2042d901c02872a4c (patch) | |
| tree | 8d38eb4409e79bf06db06520e0063dd57038d002 /mm/z3fold.c | |
| parent | c2bc26f7ca1ff1165bb6669a7a4cccc20ffd2ced (diff) | |
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>
Diffstat (limited to 'mm/z3fold.c')
| -rw-r--r-- | mm/z3fold.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/mm/z3fold.c b/mm/z3fold.c index 42f31c4b53ad..8c3bb5e508b8 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -318,16 +318,16 @@ static inline void free_handle(unsigned long handle) slots = handle_to_slots(handle); write_lock(&slots->lock); *(unsigned long *)handle = 0; - write_unlock(&slots->lock); - if (zhdr->slots == slots) + if (zhdr->slots == slots) { + write_unlock(&slots->lock); return; /* simple case, nothing else to do */ + } /* we are freeing a foreign handle if we are here */ zhdr->foreign_handles--; is_free = true; - read_lock(&slots->lock); if (!test_bit(HANDLES_ORPHANED, &slots->pool)) { - read_unlock(&slots->lock); + write_unlock(&slots->lock); return; } for (i = 0; i <= BUDDY_MASK; i++) { @@ -336,7 +336,7 @@ static inline void free_handle(unsigned long handle) break; } } - read_unlock(&slots->lock); + write_unlock(&slots->lock); if (is_free) { struct z3fold_pool *pool = slots_to_pool(slots); @@ -422,6 +422,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page, bool headless, zhdr->start_middle = 0; zhdr->cpu = -1; zhdr->foreign_handles = 0; + zhdr->mapped_count = 0; zhdr->slots = slots; zhdr->pool = pool; INIT_LIST_HEAD(&zhdr->buddy); |