[pve-devel] [PATCH qemu] fix #2874: SATA: avoid unsolicited write to sector 0 during reset

[Fiona Ebner <f.ebner@proxmox.com>]

If there is a pending DMA operation during ide_bus_reset(), the fact
that the IDEstate is already reset before the operation is canceled
can be problematic. In particular, ide_dma_cb() might be called and
then use the reset IDEstate which contains the signature after the
reset. When used to construct the IO operation this leads to
ide_get_sector() returning 0 and nsector being 1. This is particularly
bad, because a write command will thus destroy the first sector which
often contains a partition table or similar.

Upstream discussion:
https://lists.nongnu.org/archive/html/qemu-devel/2023-08/msg04239.html

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 ...cel-async-DMA-operation-before-reset.patch | 100 ++++++++++++++++++
 debian/patches/series                         |   1 +
 2 files changed, 101 insertions(+)
 create mode 100644 debian/patches/extra/0012-hw-ide-reset-cancel-async-DMA-operation-before-reset.patch

diff --git a/debian/patches/extra/0012-hw-ide-reset-cancel-async-DMA-operation-before-reset.patch b/debian/patches/extra/0012-hw-ide-reset-cancel-async-DMA-operation-before-reset.patch
new file mode 100644
index 0000000..d11ae00
--- /dev/null
+++ b/debian/patches/extra/0012-hw-ide-reset-cancel-async-DMA-operation-before-reset.patch
@@ -0,0 +1,100 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Fiona Ebner <f.ebner@proxmox.com>
+Date: Thu, 24 Aug 2023 11:22:21 +0200
+Subject: [PATCH] hw/ide: reset: cancel async DMA operation before reseting
+ state
+
+If there is a pending DMA operation during ide_bus_reset(), the fact
+that the IDEstate is already reset before the operation is canceled
+can be problematic. In particular, ide_dma_cb() might be called and
+then use the reset IDEstate which contains the signature after the
+reset. When used to construct the IO operation this leads to
+ide_get_sector() returning 0 and nsector being 1. This is particularly
+bad, because a write command will thus destroy the first sector which
+often contains a partition table or similar.
+
+Traces showing the unsolicited write happening with IDEstate
+0x5595af6949d0 being used after reset:
+
+> ahci_port_write ahci(0x5595af6923f0)[0]: port write [reg:PxSCTL] @ 0x2c: 0x00000300
+> ahci_reset_port ahci(0x5595af6923f0)[0]: reset port
+> ide_reset IDEstate 0x5595af6949d0
+> ide_reset IDEstate 0x5595af694da8
+> ide_bus_reset_aio aio_cancel
+> dma_aio_cancel dbs=0x7f64600089a0
+> dma_blk_cb dbs=0x7f64600089a0 ret=0
+> dma_complete dbs=0x7f64600089a0 ret=0 cb=0x5595acd40b30
+> ahci_populate_sglist ahci(0x5595af6923f0)[0]
+> ahci_dma_prepare_buf ahci(0x5595af6923f0)[0]: prepare buf limit=512 prepared=512
+> ide_dma_cb IDEState 0x5595af6949d0; sector_num=0 n=1 cmd=DMA WRITE
+> dma_blk_io dbs=0x7f6420802010 bs=0x5595ae2c6c30 offset=0 to_dev=1
+> dma_blk_cb dbs=0x7f6420802010 ret=0
+
+> (gdb) p *qiov
+> $11 = {iov = 0x7f647c76d840, niov = 1, {{nalloc = 1, local_iov = {iov_base = 0x0,
+>       iov_len = 512}}, {__pad = "\001\000\000\000\000\000\000\000\000\000\000",
+>       size = 512}}}
+> (gdb) bt
+> #0  blk_aio_pwritev (blk=0x5595ae2c6c30, offset=0, qiov=0x7f6420802070, flags=0,
+>     cb=0x5595ace6f0b0 <dma_blk_cb>, opaque=0x7f6420802010)
+>     at ../block/block-backend.c:1682
+> #1  0x00005595ace6f185 in dma_blk_cb (opaque=0x7f6420802010, ret=<optimized out>)
+>     at ../softmmu/dma-helpers.c:179
+> #2  0x00005595ace6f778 in dma_blk_io (ctx=0x5595ae0609f0,
+>     sg=sg@entry=0x5595af694d00, offset=offset@entry=0, align=align@entry=512,
+>     io_func=io_func@entry=0x5595ace6ee30 <dma_blk_write_io_func>,
+>     io_func_opaque=io_func_opaque@entry=0x5595ae2c6c30,
+>     cb=0x5595acd40b30 <ide_dma_cb>, opaque=0x5595af6949d0,
+>     dir=DMA_DIRECTION_TO_DEVICE) at ../softmmu/dma-helpers.c:244
+> #3  0x00005595ace6f90a in dma_blk_write (blk=0x5595ae2c6c30,
+>     sg=sg@entry=0x5595af694d00, offset=offset@entry=0, align=align@entry=512,
+>     cb=cb@entry=0x5595acd40b30 <ide_dma_cb>, opaque=opaque@entry=0x5595af6949d0)
+>     at ../softmmu/dma-helpers.c:280
+> #4  0x00005595acd40e18 in ide_dma_cb (opaque=0x5595af6949d0, ret=<optimized out>)
+>     at ../hw/ide/core.c:953
+> #5  0x00005595ace6f319 in dma_complete (ret=0, dbs=0x7f64600089a0)
+>     at ../softmmu/dma-helpers.c:107
+> #6  dma_blk_cb (opaque=0x7f64600089a0, ret=0) at ../softmmu/dma-helpers.c:127
+> #7  0x00005595ad12227d in blk_aio_complete (acb=0x7f6460005b10)
+>     at ../block/block-backend.c:1527
+> #8  blk_aio_complete (acb=0x7f6460005b10) at ../block/block-backend.c:1524
+> #9  blk_aio_write_entry (opaque=0x7f6460005b10) at ../block/block-backend.c:1594
+> #10 0x00005595ad258cfb in coroutine_trampoline (i0=<optimized out>,
+>     i1=<optimized out>) at ../util/coroutine-ucontext.c:177
+
+Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
+---
+ hw/ide/core.c | 14 +++++++-------
+ 1 file changed, 7 insertions(+), 7 deletions(-)
+
+diff --git a/hw/ide/core.c b/hw/ide/core.c
+index 08e1f0c3d7..148fccdef2 100644
+--- a/hw/ide/core.c
++++ b/hw/ide/core.c
+@@ -2513,19 +2513,19 @@ static void ide_dummy_transfer_stop(IDEState *s)
+ 
+ void ide_bus_reset(IDEBus *bus)
+ {
+-    bus->unit = 0;
+-    bus->cmd = 0;
+-    ide_reset(&bus->ifs[0]);
+-    ide_reset(&bus->ifs[1]);
+-    ide_clear_hob(bus);
+-
+-    /* pending async DMA */
++    /* pending async DMA - needs the IDEState before it is reset */
+     if (bus->dma->aiocb) {
+         trace_ide_bus_reset_aio();
+         blk_aio_cancel(bus->dma->aiocb);
+         bus->dma->aiocb = NULL;
+     }
+ 
++    bus->unit = 0;
++    bus->cmd = 0;
++    ide_reset(&bus->ifs[0]);
++    ide_reset(&bus->ifs[1]);
++    ide_clear_hob(bus);
++
+     /* reset dma provider too */
+     if (bus->dma->ops->reset) {
+         bus->dma->ops->reset(bus->dma);
diff --git a/debian/patches/series b/debian/patches/series
index 74578f6..996fa1f 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -9,6 +9,7 @@ extra/0008-raven-disable-reentrancy-detection-for-iomem.patch
 extra/0009-apic-disable-reentrancy-detection-for-apic-msi.patch
 extra/0010-migration-block-dirty-bitmap-fix-loading-bitmap-when.patch
 extra/0011-vhost-fix-the-fd-leak.patch
+extra/0012-hw-ide-reset-cancel-async-DMA-operation-before-reset.patch
 bitmap-mirror/0001-drive-mirror-add-support-for-sync-bitmap-mode-never.patch
 bitmap-mirror/0002-drive-mirror-add-support-for-conditional-and-always-.patch
 bitmap-mirror/0003-mirror-add-check-for-bitmap-mode-without-bitmap.patch
-- 
2.39.2