Fedora QA reported the following panic:
BUG: unable to handle page fault for address: 0000000040003e54
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 1082ec067 P4D 0
Oops: Oops: 0002 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted
6.19.0-0.rc4.260108gf0b9d8eb98df.34.fc43.x86_64 #1 PREEMPT(lazy)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20251119-3.fc43
11/19/2025
RIP: 0010:vmware_hypercall4.constprop.0+0x52/0x90
Code: 48 83 c4 20 5b e9 69 f0 fc fe 8b 05 a0 c1 b2 01 85 c0 74 23 b8 68 58 4d
56 b9 27 00 00 00 31 d2 bb 04 00 00 00 66 ba 58 56 ed <89> 1f 89 0e 41 89 10 5b
e9 3c f0 fc fe 6a 00 49 89 f9 45 31 c0 31
RSP: 0018:ff5eeb3240003e40 EFLAGS: 00010046
RAX: 0000000000000000 RBX: 000000000000ffca RCX: 000000000000ffac
RDX: 0000000000000000 RSI: 0000000040003e58 RDI: 0000000040003e54
RBP: ff1e05f3c1204800 R08: ff5eeb3240003e5c R09: 000000009d899c41
R10: 000000000000003d R11: ff5eeb3240003ff8 R12: 0000000000000000
R13: 00000000000000ff R14: ff1e05f3c02f9e00 R15: 000000000000000c
FS: 0000000000000000(0000) GS:ff1e05f489e40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000040003e54 CR3: 000000010841d002 CR4: 0000000000771ef0
PKRU: 55555554
Call Trace:
<IRQ>
vmmouse_report_events+0x13e/0x1b0
psmouse_handle_byte+0x15/0x60
ps2_interrupt+0x8a/0xd0
...
The panic was triggered by dereferencing a bad pointer (RDI) immediately
after a VMware hypercall for VMWARE_CMD_ABSPOINTER_DATA in the vmmouse
driver:
ffffffff82135070 <vmware_hypercall4.constprop.0>:
...
ffffffff821350ac: b8 68 58 4d 56 mov $0x564d5868,%eax
ffffffff821350b1: b9 27 00 00 00 mov $0x27,%ecx
ffffffff821350b6: 31 d2 xor %edx,%edx
ffffffff821350b8: bb 04 00 00 00 mov $0x4,%ebx
ffffffff821350bd: 66 ba 58 56 mov $0x5658,%dx
ffffffff821350c1: ed in (%dx),%eax <--
hypercall
ffffffff821350c2: 89 1f mov %ebx,(%rdi) <--
crash
Reading the disassembly shows that RDI should contain the value of a
valid kernel stack address here (0xff5eeb3240003e54). Instead it
contains 0x40003e54, suggesting the hypervisor cleared the upper 32
bits.
And indeed, Alexey discovered that QEMU's vmmouse_get_data() and
vmmouse_set_data() are only saving/restoring the lower 32 bits, while
clearing the upper 32. Fix that by changing the type of the saved data
array from uint32_t to target_ulong.
Fixes: 548df2acc6fc ("VMMouse Emulation, by Anthony Liguori.")
Reported-by: Justin Forbes <[email protected]>
Debugged-by: Alexey Makhalov <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
---
hw/i386/vmmouse.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/hw/i386/vmmouse.c b/hw/i386/vmmouse.c
index 2ae7f3a242..3bba221d5f 100644
--- a/hw/i386/vmmouse.c
+++ b/hw/i386/vmmouse.c
@@ -72,7 +72,7 @@ struct VMMouseState {
ISAKBDState *i8042;
};
-static void vmmouse_get_data(uint32_t *data)
+static void vmmouse_get_data(target_ulong *data)
{
X86CPU *cpu = X86_CPU(current_cpu);
CPUX86State *env = &cpu->env;
@@ -82,7 +82,7 @@ static void vmmouse_get_data(uint32_t *data)
data[4] = env->regs[R_ESI]; data[5] = env->regs[R_EDI];
}
-static void vmmouse_set_data(const uint32_t *data)
+static void vmmouse_set_data(const target_ulong *data)
{
X86CPU *cpu = X86_CPU(current_cpu);
CPUX86State *env = &cpu->env;
@@ -197,7 +197,7 @@ static void vmmouse_disable(VMMouseState *s)
vmmouse_remove_handler(s);
}
-static void vmmouse_data(VMMouseState *s, uint32_t *data, uint32_t size)
+static void vmmouse_data(VMMouseState *s, target_ulong *data, uint32_t size)
{
int i;
@@ -221,7 +221,7 @@ static void vmmouse_data(VMMouseState *s, uint32_t *data,
uint32_t size)
static uint32_t vmmouse_ioport_read(void *opaque, uint32_t addr)
{
VMMouseState *s = opaque;
- uint32_t data[6];
+ target_ulong data[6];
uint16_t command;
vmmouse_get_data(data);
@@ -247,7 +247,7 @@ static uint32_t vmmouse_ioport_read(void *opaque, uint32_t
addr)
vmmouse_request_absolute(s);
break;
default:
- printf("vmmouse: unknown command %x\n", data[1]);
+ printf("vmmouse: unknown command " TARGET_FMT_lx "\n", data[1]);
break;
}
break;
--
2.52.0
