sound: memory leak in snd_seq_pool_init

[Dmitry Vyukov]

Hello,

The following program causes memory leak of a 24K object allocated in
snd_seq_pool_init:

// autogenerated by syzkaller (http://github.com/google/syzkaller)
#include <pthread.h>
#include <stdint.h>
#include <string.h>
#include <sys/syscall.h>
#include <unistd.h>

long r[148];

void* thr(void* arg)
{
switch ((long)arg) {
case 0:
r[0] = syscall(SYS_mmap, 0x20000000ul, 0xe000ul, 0x3ul, 0x32ul,
0xfffffffffffffffful, 0x0ul);
break;
case 1:
r[2] = syscall(SYS_open, "/dev/snd/seq", 0x1ul, 0, 0, 0);
break;
case 2:
*(uint32_t*)0x20008a90 = (uint32_t)0x6;
*(uint32_t*)0x20008a94 = (uint32_t)0x4;
*(uint32_t*)0x20008a98 = (uint32_t)0x200;
*(uint8_t*)0x20008a9c = (uint8_t)0xfa5;
*(uint8_t*)0x20008a9d = (uint8_t)0x100000000;
*(uint8_t*)0x20008a9e = (uint8_t)0x0;
*(uint8_t*)0x20008a9f = (uint8_t)0x3;
*(uint8_t*)0x20008aa0 = (uint8_t)0x1;
*(uint8_t*)0x20008aa1 = (uint8_t)0x1;
*(uint8_t*)0x20008aa2 = (uint8_t)0x0;
*(uint8_t*)0x20008aa3 = (uint8_t)0x40;
*(uint8_t*)0x20008aa4 = (uint8_t)0x9;
*(uint8_t*)0x20008aa5 = (uint8_t)0x9;
*(uint8_t*)0x20008aa6 = (uint8_t)0x6;
*(uint8_t*)0x20008aa7 = (uint8_t)0x80;
*(uint8_t*)0x20008aa8 = (uint8_t)0x0;
*(uint8_t*)0x20008aa9 = (uint8_t)0x5d34b2c3;
*(uint8_t*)0x20008aaa = (uint8_t)0x3a7;
*(uint8_t*)0x20008aab = (uint8_t)0x9;
*(uint8_t*)0x20008aac = (uint8_t)0x8d62;
*(uint8_t*)0x20008aad = (uint8_t)0x5;
*(uint8_t*)0x20008aae = (uint8_t)0x7;
*(uint8_t*)0x20008aaf = (uint8_t)0x20;
*(uint8_t*)0x20008ab0 = (uint8_t)0x8;
*(uint8_t*)0x20008ab1 = (uint8_t)0x7;
*(uint8_t*)0x20008ab2 = (uint8_t)0xfffffffffffffffc;
*(uint8_t*)0x20008ab3 = (uint8_t)0x7;
*(uint8_t*)0x20008ab4 = (uint8_t)0x7ff;
*(uint8_t*)0x20008ab5 = (uint8_t)0x1;
*(uint8_t*)0x20008ab6 = (uint8_t)0x0;
*(uint8_t*)0x20008ab7 = (uint8_t)0x9;
*(uint8_t*)0x20008ab8 = (uint8_t)0x6;
*(uint8_t*)0x20008ab9 = (uint8_t)0xfffffffffffffe00;
*(uint8_t*)0x20008aba = (uint8_t)0x1000;
*(uint8_t*)0x20008abb = (uint8_t)0xfffffffffffffffb;
*(uint8_t*)0x20008abc = (uint8_t)0xcfd3;
*(uint8_t*)0x20008abd = (uint8_t)0x101;
*(uint8_t*)0x20008abe = (uint8_t)0x9;
*(uint8_t*)0x20008abf = (uint8_t)0xfffffffffffffffc;
*(uint8_t*)0x20008ac0 = (uint8_t)0xf2;
*(uint8_t*)0x20008ac1 = (uint8_t)0x6;
*(uint8_t*)0x20008ac2 = (uint8_t)0x0;
*(uint8_t*)0x20008ac3 = (uint8_t)0x7fffffff;
*(uint8_t*)0x20008ac4 = (uint8_t)0x4;
*(uint8_t*)0x20008ac5 = (uint8_t)0x5;
*(uint8_t*)0x20008ac6 = (uint8_t)0x4;
*(uint8_t*)0x20008ac7 = (uint8_t)0x4;
*(uint8_t*)0x20008ac8 = (uint8_t)0x20;
*(uint8_t*)0x20008ac9 = (uint8_t)0x401;
*(uint8_t*)0x20008aca = (uint8_t)0x6;
*(uint8_t*)0x20008acb = (uint8_t)0x6;
*(uint8_t*)0x20008acc = (uint8_t)0x5;
*(uint8_t*)0x20008acd = (uint8_t)0x3;
*(uint8_t*)0x20008ace = (uint8_t)0xfffffffffffffffc;
*(uint8_t*)0x20008acf = (uint8_t)0xb0c;
*(uint8_t*)0x20008ad0 = (uint8_t)0x2;
*(uint8_t*)0x20008ad1 = (uint8_t)0xfffffffffffffff9;
*(uint8_t*)0x20008ad2 = (uint8_t)0x8000;
*(uint8_t*)0x20008ad3 = (uint8_t)0x5;
*(uint8_t*)0x20008ad4 = (uint8_t)0xb0c;
*(uint8_t*)0x20008ad5 = (uint8_t)0xfffffffffffffeff;
*(uint8_t*)0x20008ad6 = (uint8_t)0x5;
*(uint8_t*)0x20008ad7 = (uint8_t)0x101;
*(uint8_t*)0x20008ad8 = (uint8_t)0xbfd;
*(uint8_t*)0x20008ad9 = (uint8_t)0x7ff;
*(uint8_t*)0x20008ada = (uint8_t)0x7f;
*(uint8_t*)0x20008adb = (uint8_t)0x5;
*(uint32_t*)0x20008adc = (uint32_t)0x6;
*(uint8_t*)0x20008ae0 = (uint8_t)0x0;
*(uint8_t*)0x20008ae1 = (uint8_t)0x0;
*(uint8_t*)0x20008ae2 = (uint8_t)0x0;
*(uint8_t*)0x20008ae3 = (uint8_t)0x0;
*(uint8_t*)0x20008ae4 = (uint8_t)0x0;
*(uint8_t*)0x20008ae5 = (uint8_t)0x0;
*(uint8_t*)0x20008ae6 = (uint8_t)0x0;
*(uint8_t*)0x20008ae7 = (uint8_t)0x0;
*(uint8_t*)0x20008ae8 = (uint8_t)0x0;
*(uint8_t*)0x20008ae9 = (uint8_t)0x0;
*(uint8_t*)0x20008aea = (uint8_t)0x0;
*(uint8_t*)0x20008aeb = (uint8_t)0x0;
*(uint8_t*)0x20008aec = (uint8_t)0x0;
*(uint8_t*)0x20008aed = (uint8_t)0x0;
*(uint8_t*)0x20008aee = (uint8_t)0x0;
*(uint8_t*)0x20008aef = (uint8_t)0x0;
*(uint8_t*)0x20008af0 = (uint8_t)0x0;
*(uint8_t*)0x20008af1 = (uint8_t)0x0;
*(uint8_t*)0x20008af2 = (uint8_t)0x0;
*(uint8_t*)0x20008af3 = (uint8_t)0x0;
*(uint8_t*)0x20008af4 = (uint8_t)0x0;
*(uint8_t*)0x20008af5 = (uint8_t)0x0;
*(uint8_t*)0x20008af6 = (uint8_t)0x0;
*(uint8_t*)0x20008af7 = (uint8_t)0x0;
*(uint8_t*)0x20008af8 = (uint8_t)0x0;
*(uint8_t*)0x20008af9 = (uint8_t)0x0;
*(uint8_t*)0x20008afa = (uint8_t)0x0;
*(uint8_t*)0x20008afb = (uint8_t)0x0;
*(uint8_t*)0x20008afc = (uint8_t)0x0;
*(uint8_t*)0x20008afd = (uint8_t)0x0;
*(uint8_t*)0x20008afe = (uint8_t)0x0;
*(uint8_t*)0x20008aff = (uint8_t)0x0;
*(uint8_t*)0x20008b00 = (uint8_t)0x0;
*(uint8_t*)0x20008b01 = (uint8_t)0x0;
*(uint8_t*)0x20008b02 = (uint8_t)0x0;
*(uint8_t*)0x20008b03 = (uint8_t)0x0;
*(uint8_t*)0x20008b04 = (uint8_t)0x0;
*(uint8_t*)0x20008b05 = (uint8_t)0x0;
*(uint8_t*)0x20008b06 = (uint8_t)0x0;
*(uint8_t*)0x20008b07 = (uint8_t)0x0;
*(uint8_t*)0x20008b08 = (uint8_t)0x0;
*(uint8_t*)0x20008b09 = (uint8_t)0x0;
*(uint8_t*)0x20008b0a = (uint8_t)0x0;
*(uint8_t*)0x20008b0b = (uint8_t)0x0;
*(uint8_t*)0x20008b0c = (uint8_t)0x0;
*(uint8_t*)0x20008b0d = (uint8_t)0x0;
*(uint8_t*)0x20008b0e = (uint8_t)0x0;
*(uint8_t*)0x20008b0f = (uint8_t)0x0;
*(uint8_t*)0x20008b10 = (uint8_t)0x0;
*(uint8_t*)0x20008b11 = (uint8_t)0x0;
*(uint8_t*)0x20008b12 = (uint8_t)0x0;
*(uint8_t*)0x20008b13 = (uint8_t)0x0;
*(uint8_t*)0x20008b14 = (uint8_t)0x0;
*(uint8_t*)0x20008b15 = (uint8_t)0x0;
*(uint8_t*)0x20008b16 = (uint8_t)0x0;
*(uint8_t*)0x20008b17 = (uint8_t)0x0;
*(uint8_t*)0x20008b18 = (uint8_t)0x0;
*(uint8_t*)0x20008b19 = (uint8_t)0x0;
*(uint8_t*)0x20008b1a = (uint8_t)0x0;
*(uint8_t*)0x20008b1b = (uint8_t)0x0;
r[131] =
syscall(SYS_ioctl, r[2], 0xc08c5332ul, 0x20008a90ul, 0, 0, 0);
break;
case 3:
*(uint32_t*)0x20009fd0 = (uint32_t)0x30;
*(uint32_t*)0x20009fd4 = (uint32_t)0xfff;
*(uint64_t*)0x20009fd8 = (uint64_t)0x0;
*(uint64_t*)0x20009fe0 = (uint64_t)0x1ce;
*(uint64_t*)0x20009fe8 = (uint64_t)0x2;
*(uint64_t*)0x20009ff0 = (uint64_t)0xff;
*(uint32_t*)0x20009ff8 = (uint32_t)0x10001;
r[139] = syscall(SYS_write, r[2], 0x20009fd0ul, 0x30ul, 0, 0, 0);
break;
case 4:
*(uint32_t*)0x2000bb13 = (uint32_t)0x30;
*(uint32_t*)0x2000bb17 = (uint32_t)0x2;
*(uint64_t*)0x2000bb1b = (uint64_t)0x0;
*(uint64_t*)0x2000bb23 = (uint64_t)0x53;
*(uint64_t*)0x2000bb2b = (uint64_t)0xfffffffffffffbff;
*(uint64_t*)0x2000bb33 = (uint64_t)0x5;
*(uint32_t*)0x2000bb3b = (uint32_t)0x5;
r[147] = syscall(SYS_write, r[2], 0x2000bb13ul, 0x30ul, 0, 0, 0);
break;
}
return 0;
}

int main()
{
long i;
pthread_t th[5];

memset(r, -1, sizeof(r));
for (i = 0; i < 5; i++) {
pthread_create(&th[i], 0, thr, (void*)i);
usleep(10000);
}
for (i = 0; i < 5; i++) {
pthread_create(&th[i], 0, thr, (void*)i);
if (i % 2 == 0)
usleep(10000);
}
usleep(100000);
return 0;
}



unreferenced object 0xffffc90003663000 (size 24000):
comm "a.out", pid 1770, jiffies 4295717383 (age 7.217s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<ffffffff86644303>] kmemleak_alloc+0x63/0xa0 mm/kmemleak.c:916
[<ffffffff81720da9>] __vmalloc_node_range+0x469/0x640 mm/vmalloc.c:1682
[< inline >] __vmalloc_node mm/vmalloc.c:1710
[< inline >] __vmalloc_node_flags mm/vmalloc.c:1724
[<ffffffff8172104b>] vmalloc+0x5b/0x70 mm/vmalloc.c:1739
[<ffffffff852b92cb>] snd_seq_pool_init+0xbb/0x300
sound/core/seq/seq_memory.c:389
[<ffffffff852b5ff4>] snd_seq_write+0x4d4/0x570
sound/core/seq/seq_clientmgr.c:1029
[<ffffffff817bbfc3>] __vfs_write+0x113/0x4b0 fs/read_write.c:528
[<ffffffff817bda87>] vfs_write+0x167/0x4a0 fs/read_write.c:577
[< inline >] SYSC_write fs/read_write.c:624
[<ffffffff817c0d71>] SyS_write+0x111/0x220 fs/read_write.c:616
[<ffffffff866613f6>] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185
[<ffffffffffffffff>] 0xffffffffffffffff


On commit 388f7b1d6e8ca06762e2454d28d6c3c55ad0fe95 (4.5-rc3)

[Takashi Iwai]

Hm, this looks like the issue triggered by concurrent writes to the
same client. Does the patch fix the problem?


thanks,

Takashi

---
diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c
index 801076687bb1..c850345c43b5 100644
--- a/sound/core/seq/seq_memory.c
+++ b/sound/core/seq/seq_memory.c
@@ -383,15 +383,20 @@ int snd_seq_pool_init(struct snd_seq_pool *pool)

if (snd_BUG_ON(!pool))
return -EINVAL;
- if (pool->ptr) /* should be atomic? */
- return 0;

- pool->ptr = vmalloc(sizeof(struct snd_seq_event_cell) * pool->size);
- if (!pool->ptr)
+ cellptr = vmalloc(sizeof(struct snd_seq_event_cell) * pool->size);
+ if (!cellptr)
return -ENOMEM;

/* add new cells to the free cell list */
spin_lock_irqsave(&pool->lock, flags);
+ if (pool->ptr) {
+ spin_unlock_irqrestore(&pool->lock, flags);
+ vfree(cellptr);
+ return 0;
+ }
+
+ pool->ptr = cellptr;
pool->free = NULL;

for (cell = 0; cell < pool->size; cell++) {

[Dmitry Vyukov]

Yes, it fixes the leak for me.

Tested-by: Dmitry Vyukov <dvy...@google.com>

[Takashi Iwai]

On Mon, 15 Feb 2016 16:15:49 +0100,
Dmitry Vyukov wrote:
>
> > Hm, this looks like the issue triggered by concurrent writes to the
> > same client. Does the patch fix the problem?
>
> Yes, it fixes the leak for me.
>
> Tested-by: Dmitry Vyukov <dvy...@google.com>

Thanks for the quick test. FWIW, below is the final patch I'm going
to merge.


Takashi

-- 8< --
From: Takashi Iwai <ti...@suse.de>
Subject: [PATCH] ALSA: seq: Fix leak of pool buffer at concurrent writes

When multiple concurrent writes happen on the ALSA sequencer device
right after the open, it may try to allocate vmalloc buffer for each
write and leak some of them. It's because the presence check and the
assignment of the buffer is done outside the spinlock for the pool.

The fix is to move the check and the assignment into the spinlock.

(The current implementation is suboptimal, as there can be multiple
unnecessary vmallocs because the allocation is done before the check
in the spinlock. But the pool size is already checked beforehand, so
this isn't a big problem; that is, the only possible path is the
multiple writes before any pool assignment, and practically seen, the
current coverage should be "good enough".)

The issue was triggered by syzkaller fuzzer.

BugLink: http://lkml.kernel.org/r/CACT4Y+bSzazpXNvtAr=WXaL8hptqjHwqEyFA+VN2AWEx=au...@mail.gmail.com
Reported-by: Dmitry Vyukov <dvy...@google.com>
Tested-by: Dmitry Vyukov <dvy...@google.com>
Cc: <sta...@vger.kernel.org>
Signed-off-by: Takashi Iwai <ti...@suse.de>
---
sound/core/seq/seq_memory.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

--
2.7.1