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[PULL 3/3] block: fix bdrv_aio_cancel() for ENOMEDIUM requests
From: |
Max Reitz |
Subject: |
[PULL 3/3] block: fix bdrv_aio_cancel() for ENOMEDIUM requests |
Date: |
Tue, 21 Jul 2020 13:49:20 +0200 |
From: Stefan Hajnoczi <stefanha@redhat.com>
bdrv_aio_cancel() calls aio_poll() on the AioContext for the given I/O
request until it has completed. ENOMEDIUM requests are special because
there is no BlockDriverState when the drive has no medium!
Define a .get_aio_context() function for BlkAioEmAIOCB requests so that
bdrv_aio_cancel() can find the AioContext where the completion BH is
pending. Without this function bdrv_aio_cancel() aborts on ENOMEDIUM
requests!
libFuzzer triggered the following assertion:
cat << EOF | qemu-system-i386 -M pc-q35-5.0 \
-nographic -monitor none -serial none \
-qtest stdio -trace ide\*
outl 0xcf8 0x8000fa24
outl 0xcfc 0xe106c000
outl 0xcf8 0x8000fa04
outw 0xcfc 0x7
outl 0xcf8 0x8000fb20
write 0x0 0x3 0x2780e7
write 0xe106c22c 0xd 0x1130c218021130c218021130c2
write 0xe106c218 0x15 0x110010110010110010110010110010110010110010
EOF
ide_exec_cmd IDE exec cmd: bus 0x56170a77a2b8; state 0x56170a77a340; cmd 0xe7
ide_reset IDEstate 0x56170a77a340
Aborted (core dumped)
(gdb) bt
#1 0x00007ffff4f93895 in abort () at /lib64/libc.so.6
#2 0x0000555555dc6c00 in bdrv_aio_cancel (acb=0x555556765550) at
block/io.c:2745
#3 0x0000555555dac202 in blk_aio_cancel (acb=0x555556765550) at
block/block-backend.c:1546
#4 0x0000555555b1bd74 in ide_reset (s=0x555557213340) at hw/ide/core.c:1318
#5 0x0000555555b1e3a1 in ide_bus_reset (bus=0x5555572132b8) at
hw/ide/core.c:2422
#6 0x0000555555b2aa27 in ahci_reset_port (s=0x55555720eb50, port=2) at
hw/ide/ahci.c:650
#7 0x0000555555b29fd7 in ahci_port_write (s=0x55555720eb50, port=2,
offset=44, val=16) at hw/ide/ahci.c:360
#8 0x0000555555b2a564 in ahci_mem_write (opaque=0x55555720eb50, addr=556,
val=16, size=1) at hw/ide/ahci.c:513
#9 0x000055555598415b in memory_region_write_accessor (mr=0x55555720eb80,
addr=556, value=0x7fffffffb838, size=1, shift=0, mask=255, attrs=...) at
softmmu/memory.c:483
Looking at bdrv_aio_cancel:
2728 /* async I/Os */
2729
2730 void bdrv_aio_cancel(BlockAIOCB *acb)
2731 {
2732 qemu_aio_ref(acb);
2733 bdrv_aio_cancel_async(acb);
2734 while (acb->refcnt > 1) {
2735 if (acb->aiocb_info->get_aio_context) {
2736 aio_poll(acb->aiocb_info->get_aio_context(acb), true);
2737 } else if (acb->bs) {
2738 /* qemu_aio_ref and qemu_aio_unref are not thread-safe, so
2739 * assert that we're not using an I/O thread. Thread-safe
2740 * code should use bdrv_aio_cancel_async exclusively.
2741 */
2742 assert(bdrv_get_aio_context(acb->bs) ==
qemu_get_aio_context());
2743 aio_poll(bdrv_get_aio_context(acb->bs), true);
2744 } else {
2745 abort(); <===============
2746 }
2747 }
2748 qemu_aio_unref(acb);
2749 }
Fixes: 02c50efe08736116048d5fc355043080f4d5859c ("block: Add
bdrv_aio_cancel_async")
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Buglink: https://bugs.launchpad.net/qemu/+bug/1878255
Originally-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200720100141.129739-1-stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
block/block-backend.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/block/block-backend.c b/block/block-backend.c
index 0bf0188133..3a13cb5f0b 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1394,8 +1394,16 @@ typedef struct BlkAioEmAIOCB {
bool has_returned;
} BlkAioEmAIOCB;
+static AioContext *blk_aio_em_aiocb_get_aio_context(BlockAIOCB *acb_)
+{
+ BlkAioEmAIOCB *acb = container_of(acb_, BlkAioEmAIOCB, common);
+
+ return blk_get_aio_context(acb->rwco.blk);
+}
+
static const AIOCBInfo blk_aio_em_aiocb_info = {
.aiocb_size = sizeof(BlkAioEmAIOCB),
+ .get_aio_context = blk_aio_em_aiocb_get_aio_context,
};
static void blk_aio_complete(BlkAioEmAIOCB *acb)
--
2.26.2