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[Qemu-devel] [PATCH] target-i386: Fixed syscall posssible segfault
From: |
Stanislav Shmarov |
Subject: |
[Qemu-devel] [PATCH] target-i386: Fixed syscall posssible segfault |
Date: |
Tue, 13 Sep 2016 16:23:28 +0300 |
In user-mode emulation env->idt.base memory is
allocated in linux-user/main.c with
size 8*512 = 4096 (for 64-bit).
When fake interrupt EXCP_SYSCALL is thrown
do_interrupt_user checks destination privilege level
for this fake exception, and tries to read 4 bytes
at address base + (256 * 2^4)=4096, that causes
segfault.
Privlege level was checked only for int's, so lets
read dpl from memory only for this case.
Signed-off-by: Stanislav Shmarov <address@hidden>
---
target-i386/seg_helper.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff --git a/target-i386/seg_helper.c b/target-i386/seg_helper.c
index 6cbdf17..fb79f31 100644
--- a/target-i386/seg_helper.c
+++ b/target-i386/seg_helper.c
@@ -1137,25 +1137,27 @@ static void do_interrupt_real(CPUX86State *env, int
intno, int is_int,
static void do_interrupt_user(CPUX86State *env, int intno, int is_int,
int error_code, target_ulong next_eip)
{
- SegmentCache *dt;
- target_ulong ptr;
- int dpl, cpl, shift;
- uint32_t e2;
+ if (is_int) {
+ SegmentCache *dt;
+ target_ulong ptr;
+ int dpl, cpl, shift;
+ uint32_t e2;
- dt = &env->idt;
- if (env->hflags & HF_LMA_MASK) {
- shift = 4;
- } else {
- shift = 3;
- }
- ptr = dt->base + (intno << shift);
- e2 = cpu_ldl_kernel(env, ptr + 4);
+ dt = &env->idt;
+ if (env->hflags & HF_LMA_MASK) {
+ shift = 4;
+ } else {
+ shift = 3;
+ }
+ ptr = dt->base + (intno << shift);
+ e2 = cpu_ldl_kernel(env, ptr + 4);
- dpl = (e2 >> DESC_DPL_SHIFT) & 3;
- cpl = env->hflags & HF_CPL_MASK;
- /* check privilege if software int */
- if (is_int && dpl < cpl) {
- raise_exception_err(env, EXCP0D_GPF, (intno << shift) + 2);
+ dpl = (e2 >> DESC_DPL_SHIFT) & 3;
+ cpl = env->hflags & HF_CPL_MASK;
+ /* check privilege if software int */
+ if (dpl < cpl) {
+ raise_exception_err(env, EXCP0D_GPF, (intno << shift) + 2);
+ }
}
/* Since we emulate only user space, we cannot do more than
--
1.9.3
- [Qemu-devel] [PATCH] target-i386: Fixed syscall posssible segfault,
Stanislav Shmarov <=