Commit 885b7c44 authored by Stanislav Shmarov's avatar Stanislav Shmarov Committed by Paolo Bonzini
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target-i386: Fixed syscall posssible segfault 



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: default avatarStanislav Shmarov <snarpix@gmail.com>
Message-Id: <1473773008-2588376-1-git-send-email-snarpix@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 89d0a64f

target-i386/seg_helper.c

+19 −17
Original line number Diff line number Diff line
@@ -1137,6 +1137,7 @@ 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)

{

    if (is_int) {

        SegmentCache *dt;

        target_ulong ptr;

        int dpl, cpl, shift;
@@ -1154,9 +1155,10 @@ static void do_interrupt_user(CPUX86State *env, int intno, int is_int, 
        dpl = (e2 >> DESC_DPL_SHIFT) & 3;

        cpl = env->hflags & HF_CPL_MASK;

        /* check privilege if software int */

    if (is_int && dpl < cpl) {

        if (dpl < cpl) {

            raise_exception_err(env, EXCP0D_GPF, (intno << shift) + 2);

        }

    }



    /* Since we emulate only user space, we cannot do more than

       exiting the emulation with the suitable exception and error