[PATCH v2] lzo: fix ip overrun during compress.

Yueyi Li
2018-11-28T07:31:33Z

It`s possible ip overrun in lzo1x_1_do_compress() when compressed page is
point to the end of memory and which virtual address is 0xfffffffffffff000.
Leading to a NULL pointer access during the get_unaligned_le32(ip).

Fix this panic:
[ 2738.034508] Unable to handle kernel NULL pointer dereference at virtual address 00000009
[ 2738.034515] Mem abort info:
[ 2738.034518] Exception class = DABT (current EL), IL = 32 bits
[ 2738.034520] SET = 0, FnV = 0
[ 2738.034523] EA = 0, S1PTW = 0
[ 2738.034524] FSC = 5
[ 2738.034526] Data abort info:
[ 2738.034528] ISV = 0, ISS = 0x00000005
[ 2738.034530] CM = 0, WnR = 0
[ 2738.034533] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffff94cee000
[ 2738.034535] [0000000000000009] *pgd=0000000000000000, *pud=0000000000000000
...
[ 2738.034592] pc : lzo1x_1_do_compress+0x198/0x610
[ 2738.034595] lr : lzo1x_1_compress+0x98/0x3d8
[ 2738.034597] sp : ffffff801caa3470 pstate : 00c00145
[ 2738.034598] x29: ffffff801caa3500 x28: 0000000000001000
[ 2738.034601] x27: 0000000000001000 x26: fffffffffffff000
[ 2738.034604] x25: ffffffff4ebc0000 x24: 0000000000000000
[ 2738.034607] x23: 000000000000004c x22: fffffffffffff7b8
[ 2738.034610] x21: ffffffff2e2ee0b3 x20: ffffffff2e2ee0bb
[ 2738.034612] x19: 0000000000000fcc x18: fffffffffffff84a
[ 2738.034615] x17: 00000000801b03d6 x16: 0000000000000782
[ 2738.034618] x15: ffffffff2e2ee0bf x14: fffffffffffffff0
[ 2738.034620] x13: 000000000000000f x12: 0000000000000020
[ 2738.034623] x11: 000000001824429d x10: ffffffffffffffec
[ 2738.034626] x9 : 0000000000000009 x8 : 0000000000000000
[ 2738.034628] x7 : 0000000000000868 x6 : 0000000000000434
[ 2738.034631] x5 : ffffffff4ebc0000 x4 : 0000000000000000
[ 2738.034633] x3 : ffffff801caa3510 x2 : ffffffff2e2ee000
[ 2738.034636] x1 : 0000000000000000 x0 : fffffffffffff000
...
[ 2738.034717] Process kworker/u16:1 (pid: 8705, stack limit = 0xffffff801caa0000)
[ 2738.034720] Call trace:
[ 2738.034722] lzo1x_1_do_compress+0x198/0x610
[ 2738.034725] lzo_compress+0x48/0x88
[ 2738.034729] crypto_compress+0x14/0x20
[ 2738.034733] zcomp_compress+0x2c/0x38
[ 2738.034736] zram_bvec_rw+0x3d0/0x860
[ 2738.034738] zram_rw_page+0x88/0xe0
[ 2738.034742] bdev_write_page+0x70/0xc0
[ 2738.034745] __swap_writepage+0x58/0x3f8
[ 2738.034747] swap_writepage+0x40/0x50
[ 2738.034750] shrink_page_list+0x4fc/0xe58
[ 2738.034753] reclaim_pages_from_list+0xa0/0x150
[ 2738.034756] reclaim_pte_range+0x18c/0x1f8
[ 2738.034759] __walk_page_range+0xf8/0x1e0
[ 2738.034762] walk_page_range+0xf8/0x130
[ 2738.034765] reclaim_task_anon+0xcc/0x168
[ 2738.034767] swap_fn+0x438/0x668
[ 2738.034771] process_one_work+0x1fc/0x460
[ 2738.034773] worker_thread+0x2d0/0x478
[ 2738.034775] kthread+0x110/0x120
[ 2738.034778] ret_from_fork+0x10/0x18
[ 2738.034781] Code: 3800167f 54ffffa8 d100066f 14000031 (b9400131)
[ 2738.034784] ---[ end trace 9b5cca106f0e54d1 ]---
[ 2738.035473] Kernel panic - not syncing: Fatal exception

crash> dis lzo1x_1_do_compress+100 3 -l
../kernel/msm-4.14/lib/lzo/lzo1x_compress.c: 44
0xffffff8dec8c6af4 <lzo1x_1_do_compress+100>: cmp x9, x10
0xffffff8dec8c6af8 <lzo1x_1_do_compress+104>: b.cc 0xffffff8dec8c6c28
0xffffff8dec8c6afc <lzo1x_1_do_compress+108>: b 0xffffff8dec8c7094

crash> dis lzo1x_1_do_compress+0x198
0xffffff8dec8c6c28 <lzo1x_1_do_compress+408>: ldr w17, [x9]

ip = x9 = 0x0000000000000009 is overflow.

Signed-off-by: liyueyi <liyueyi@live.com>
---
lib/lzo/lzo1x_compress.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/lib/lzo/lzo1x_compress.c b/lib/lzo/lzo1x_compress.c
index 236eb21..b15082b 100644
--- a/lib/lzo/lzo1x_compress.c
+++ b/lib/lzo/lzo1x_compress.c
@@ -17,6 +17,9 @@
#include <linux/lzo.h>
#include "lzodefs.h"

+#define OVERFLOW_ADD_CHECK(a, b) \
+ (((a) + (b)) < (a))
+
static noinline size_t
lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
unsigned char *out, size_t *out_len,
@@ -39,6 +42,8 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
size_t t, m_len, m_off;
u32 dv;
literal:
+ if (unlikely(OVERFLOW_ADD_CHECK(ip, 1 + ((ip - ii) >> 5))))
+ break;
ip += 1 + ((ip - ii) >> 5);
next:
if (unlikely(ip >= ip_end))
@@ -99,7 +104,8 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
m_len += 8;
v = get_unaligned((const u64 *) (ip + m_len)) ^
get_unaligned((const u64 *) (m_pos + m_len));
- if (unlikely(ip + m_len >= ip_end))
+ if (unlikely(OVERFLOW_ADD_CHECK(ip, m_len)
+ || (ip + m_len >= ip_end)))
goto m_len_done;
} while (v == 0);
}
@@ -124,7 +130,8 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
m_len += 4;
v = get_unaligned((const u32 *) (ip + m_len)) ^
get_unaligned((const u32 *) (m_pos + m_len));
- if (unlikely(ip + m_len >= ip_end))
+ if (unlikely(OVERFLOW_ADD_CHECK(ip, m_len)
+ || (ip + m_len >= ip_end)))
goto m_len_done;
} while (v == 0);
}
@@ -160,7 +167,8 @@ lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
if (ip[m_len] != m_pos[m_len])
break;
m_len += 1;
- if (unlikely(ip + m_len >= ip_end))
+ if (unlikely(OVERFLOW_ADD_CHECK(ip, m_len)
+ || (ip + m_len >= ip_end)))
goto m_len_done;
} while (ip[m_len] == m_pos[m_len]);
}
--
2.7.4