Paul Gofman : ntdll: Avoid overwriting parameters with context in call_user_apc_dispatcher() on x86.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 2002aa15f476b4bb9039d5e47dfa2e3c0be58ee3
URL:    https://source.winehq.org/git/wine.git/?a=commit;h=2002aa15f476b4bb9039d5e47...

Author: Paul Gofman <pgofman(a)codeweavers.com>
Date:   Thu Nov 12 17:20:10 2020 +0300

ntdll: Avoid overwriting parameters with context in call_user_apc_dispatcher() on x86.

Fixes crash in 32 bit kernel32 file test. The crash is not always reproducible
as the issue depends on stack layout.

Signed-off-by: Paul Gofman <pgofman(a)codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard(a)winehq.org>

---

 dlls/ntdll/unix/signal_i386.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/dlls/ntdll/unix/signal_i386.c b/dlls/ntdll/unix/signal_i386.c
index 4d8eeb2072c..58b79940773 100644
--- a/dlls/ntdll/unix/signal_i386.c
+++ b/dlls/ntdll/unix/signal_i386.c
@@ -1688,15 +1688,18 @@ __ASM_GLOBAL_FUNC( call_user_apc_dispatcher,
                    "movl %esp,%ebx\n\t"
                    "cmpl %esp,%esi\n\t"
                    "cmovbl %esi,%esp\n\t"
+                   "pushl 20(%ebx)\n\t"          /* func */
+                   "pushl 16(%ebx)\n\t"          /* arg2 */
+                   "pushl 12(%ebx)\n\t"          /* arg1 */
+                   "movl 8(%ebx),%ebx\n\t"       /* ctx */
                    "movl $0x00010007,(%esi)\n\t" /* context.ContextFlags = CONTEXT_FULL */
                    "pushl %esi\n\t"              /* context */
                    "pushl $0xfffffffe\n\t"
                    "call " __ASM_STDCALL("NtGetContextThread",8) "\n\t"
                    "movl $0xc0,0xb0(%esi)\n"     /* context.Eax = STATUS_USER_APC */
-                   "movl 20(%ebx),%eax\n\t"      /* func */
-                   "movl 16(%ebx),%ecx\n\t"      /* arg2 */
-                   "movl 12(%ebx),%edx\n\t"      /* arg1 */
-                   "movl 8(%ebx),%ebx\n\t"       /* ctx */
+                   "popl %edx\n\t"
+                   "popl %ecx\n\t"
+                   "popl %eax\n\t"
                    "leal -20(%esi),%esp\n\t"
                    "movl %eax,16(%esp)\n"        /* func */
                    "2:\tmovl %ecx,12(%esp)\n\t"  /* arg2 */