Hello Dmitry On Thu, 13 Jun 2019 20:12:06 +0800 Dmitry Vyukov wrote: > On Thu, Jun 13, 2019 at 2:07 PM Hillf Danton <hdanton@xxxxxxxx> wrote: > > > > Hello Jason > > > > On Thu, 13 Jun 2019 17:10:39 +0800 Jason Wang wrote: > > > > > > This is basically a kfree(ubuf) after the second vhost_net_flush() in > > > vhost_net_release(). > > > > > Fairly good catch. > > > > > Could you please post a formal patch? > > > > > I'd like very much to do that; but I wont, I am afraid, until I collect a > > Tested-by because of reproducer without a cutting edge. > > You can easily collect Tested-by from syzbot for any bug with a reproducer;) > https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches > Thank you for the light you are casting. Here it goes. --->8-------- From: Hillf Danton <hdanton@xxxxxxxx> Subject: [PATCH] vhost: fix memory leak in vhost_net_release syzbot found the following crash on: HEAD commit: 788a0249 Merge tag 'arc-5.2-rc4' of git://git.kernel.org/p.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?xdc9ea6a00000 kernel config: https://syzkaller.appspot.com/x/.config?x�73825cbdc7326 dashboard link: https://syzkaller.appspot.com/bug?extid89f0c7e45efd7bb643 compiler: gcc (GCC) 9.0.0 20181231 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?xb31761a00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x4892c1a00000 udit: type00 audit(1559768703.229:36): avc: denied { map } for pidq16 comm="syz-executor330" path="/root/syz-executor330334897" dev="sda1" ino461 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1 executing program executing program BUG: memory leak unreferenced object 0xffff88812421fe40 (size 64): comm "syz-executor330", pid 7117, jiffies 4294949245 (age 13.030s) hex dump (first 32 bytes): 01 00 00 00 20 69 6f 63 00 00 00 00 64 65 76 2f .... ioc....dev/ 50 fe 21 24 81 88 ff ff 50 fe 21 24 81 88 ff ff P.!$....P.!$.... backtrace: [<00000000ae0c4ae0>] kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline] [<00000000ae0c4ae0>] slab_post_alloc_hook mm/slab.h:439 [inline] [<00000000ae0c4ae0>] slab_alloc mm/slab.c:3326 [inline] [<00000000ae0c4ae0>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553 [<0000000079ebab38>] kmalloc include/linux/slab.h:547 [inline] [<0000000079ebab38>] vhost_net_ubuf_alloc drivers/vhost/net.c:241 [inline] [<0000000079ebab38>] vhost_net_set_backend drivers/vhost/net.c:1534 [inline] [<0000000079ebab38>] vhost_net_ioctl+0xb43/0xc10 drivers/vhost/net.c:1716 [<000000009f6204a2>] vfs_ioctl fs/ioctl.c:46 [inline] [<000000009f6204a2>] file_ioctl fs/ioctl.c:509 [inline] [<000000009f6204a2>] do_vfs_ioctl+0x62a/0x810 fs/ioctl.c:696 [<00000000b45866de>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713 [<00000000dfb41eb8>] __do_sys_ioctl fs/ioctl.c:720 [inline] [<00000000dfb41eb8>] __se_sys_ioctl fs/ioctl.c:718 [inline] [<00000000dfb41eb8>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718 [<0000000049c1f547>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:301 [<0000000029cc8ca7>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 BUG: memory leak unreferenced object 0xffff88812421fa80 (size 64): comm "syz-executor330", pid 7130, jiffies 4294949755 (age 7.930s) hex dump (first 32 bytes): 01 00 00 00 01 00 00 00 00 00 00 00 2f 76 69 72 ............/vir 90 fa 21 24 81 88 ff ff 90 fa 21 24 81 88 ff ff ..!$......!$.... backtrace: [<00000000ae0c4ae0>] kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline] [<00000000ae0c4ae0>] slab_post_alloc_hook mm/slab.h:439 [inline] [<00000000ae0c4ae0>] slab_alloc mm/slab.c:3326 [inline] [<00000000ae0c4ae0>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553 [<0000000079ebab38>] kmalloc include/linux/slab.h:547 [inline] [<0000000079ebab38>] vhost_net_ubuf_alloc drivers/vhost/net.c:241 [inline] [<0000000079ebab38>] vhost_net_set_backend drivers/vhost/net.c:1534 [inline] [<0000000079ebab38>] vhost_net_ioctl+0xb43/0xc10 drivers/vhost/net.c:1716 [<000000009f6204a2>] vfs_ioctl fs/ioctl.c:46 [inline] [<000000009f6204a2>] file_ioctl fs/ioctl.c:509 [inline] [<000000009f6204a2>] do_vfs_ioctl+0x62a/0x810 fs/ioctl.c:696 [<00000000b45866de>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713 [<00000000dfb41eb8>] __do_sys_ioctl fs/ioctl.c:720 [inline] [<00000000dfb41eb8>] __se_sys_ioctl fs/ioctl.c:718 [inline] [<00000000dfb41eb8>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718 [<0000000049c1f547>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:301 [<0000000029cc8ca7>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 End of syzbot report. The function vhost_net_ubuf_alloc() appears in the two cases of dump info, for pid 7130 and 7117, suggesting that it is ubuf leak. Since commit c38e39c378f4 ("vhost-net: fix use-after-free in vhost_net_flush") the function vhost_net_flush() had been no longer releasing ubuf. Freeing the slab after the last flush in the release path fixes it. Fixes: c38e39c378f4 ("vhost-net: fix use-after-free in vhost_net_flush") Reported-by: Syzbot <syzbot+0789f0c7e45efd7bb643@xxxxxxxxxxxxxxxxxxxxxxxxx> Suggested-by: Jason Wang <jasowang@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Asias He <asias@xxxxxxxxxx> Signed-off-by: Hillf Danton <hdanton@xxxxxxxx> --- This is sent only for collecting Tested-by. drivers/vhost/net.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 3beb401..22fae0a 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -1404,6 +1404,7 @@ static int vhost_net_release(struct inode *inode, struct file *f) /* We do an extra flush before freeing memory, * since jobs can re-queue themselves. */ vhost_net_flush(n); + kfree(n->vqs[VHOST_NET_VQ_TX].ubufs); kfree(n->vqs[VHOST_NET_VQ_RX].rxq.queue); kfree(n->vqs[VHOST_NET_VQ_TX].xdp); kfree(n->dev.vqs); --
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