From 5abeebb1306c520895fb72e66a9d0390c534f1f4 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Mon, 4 Jul 2011 14:07:50 +0200 Subject: [PATCH] ide: Ignore reads during PIO in and writes during PIO out This fixes https://bugs.launchpad.net/qemu/+bug/786209: When the DRQ_STAT bit is set, the IDE core permits both data reads and data writes, regardless of whether the current transfer was initiated as a read or write. This potentially leaks uninitialized host memory into the guest, if, before doing anything else to an IDE device, the guest begins a write transaction (e.g. WIN_WRITE), but then *reads* from the IO port instead of writing to it. Signed-off-by: Kevin Wolf Reviewed-by: Markus Armbruster --- hw/ide/core.c | 44 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 36 insertions(+), 8 deletions(-) diff --git a/hw/ide/core.c b/hw/ide/core.c index ca17a43..a29ae9f 100644 --- a/hw/ide/core.c +++ b/hw/ide/core.c @@ -56,6 +56,7 @@ static const int smart_attributes[][12] = { }; static int ide_handle_rw_error(IDEState *s, int error, int op); +static void ide_dummy_transfer_stop(IDEState *s); static void padstr(char *str, const char *src, int len) { @@ -1532,15 +1533,36 @@ void ide_cmd_write(void *opaque, uint32_t addr, uint32_t val) bus->cmd = val; } +/* + * Returns true if the running PIO transfer is a PIO out (i.e. data is + * transferred from the device to the guest), false if it's a PIO in + */ +static bool ide_is_pio_out(IDEState *s) +{ + if (s->end_transfer_func == ide_sector_write || + s->end_transfer_func == ide_atapi_cmd) { + return false; + } else if (s->end_transfer_func == ide_sector_read || + s->end_transfer_func == ide_transfer_stop || + s->end_transfer_func == ide_atapi_cmd_reply_end || + s->end_transfer_func == ide_dummy_transfer_stop) { + return true; + } + + abort(); +} + void ide_data_writew(void *opaque, uint32_t addr, uint32_t val) { IDEBus *bus = opaque; IDEState *s = idebus_active_if(bus); uint8_t *p; - /* PIO data access allowed only when DRQ bit is set */ - if (!(s->status & DRQ_STAT)) + /* PIO data access allowed only when DRQ bit is set. The result of a write + * during PIO out is indeterminate, just ignore it. */ + if (!(s->status & DRQ_STAT) || ide_is_pio_out(s)) { return; + } p = s->data_ptr; *(uint16_t *)p = le16_to_cpu(val); @@ -1557,9 +1579,11 @@ uint32_t ide_data_readw(void *opaque, uint32_t addr) uint8_t *p; int ret; - /* PIO data access allowed only when DRQ bit is set */ - if (!(s->status & DRQ_STAT)) + /* PIO data access allowed only when DRQ bit is set. The result of a read + * during PIO in is indeterminate, return 0 and don't move forward. */ + if (!(s->status & DRQ_STAT) || !ide_is_pio_out(s)) { return 0; + } p = s->data_ptr; ret = cpu_to_le16(*(uint16_t *)p); @@ -1576,9 +1600,11 @@ void ide_data_writel(void *opaque, uint32_t addr, uint32_t val) IDEState *s = idebus_active_if(bus); uint8_t *p; - /* PIO data access allowed only when DRQ bit is set */ - if (!(s->status & DRQ_STAT)) + /* PIO data access allowed only when DRQ bit is set. The result of a write + * during PIO out is indeterminate, just ignore it. */ + if (!(s->status & DRQ_STAT) || ide_is_pio_out(s)) { return; + } p = s->data_ptr; *(uint32_t *)p = le32_to_cpu(val); @@ -1595,9 +1621,11 @@ uint32_t ide_data_readl(void *opaque, uint32_t addr) uint8_t *p; int ret; - /* PIO data access allowed only when DRQ bit is set */ - if (!(s->status & DRQ_STAT)) + /* PIO data access allowed only when DRQ bit is set. The result of a read + * during PIO in is indeterminate, return 0 and don't move forward. */ + if (!(s->status & DRQ_STAT) || !ide_is_pio_out(s)) { return 0; + } p = s->data_ptr; ret = cpu_to_le32(*(uint32_t *)p); -- 2.7.4