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ntdll: Check for invalid %gs value in 32-bit code. 

Suggested by Alessandro Pignotti.
This commit is contained in:
Alexandre Julliard 2013-02-12 15:21:15 +01:00
parent 99d89b347f
commit 64ddb263d2
1 changed files with 43 additions and 0 deletions
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43
dlls/ntdll/signal_i386.c
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@ -1507,6 +1507,47 @@ static inline DWORD is_privileged_instr( CONTEXT *context )
}
}
/***********************************************************************
* check_invalid_gs
*
* Check for fault caused by invalid %gs value (some copy protection schemes mess with it).
*/
static inline BOOL check_invalid_gs( CONTEXT *context )
{
unsigned int prefix_count = 0;
const BYTE *instr = (BYTE *)context->Eip;
WORD system_gs = ntdll_get_thread_data()->gs;
if (context->SegGs == system_gs) return FALSE;
if (!wine_ldt_is_system( context->SegCs )) return FALSE;
/* only handle faults in system libraries */
if (virtual_is_valid_code_address( instr, 1 )) return FALSE;
for (;;) switch(*instr)
{
/* instruction prefixes */
case 0x2e: /* %cs: */
case 0x36: /* %ss: */
case 0x3e: /* %ds: */
case 0x26: /* %es: */
case 0x64: /* %fs: */
case 0x66: /* opcode size */
case 0x67: /* addr size */
case 0xf0: /* lock */
case 0xf2: /* repne */
case 0xf3: /* repe */
if (++prefix_count >= 15) return FALSE;
instr++;
continue;
case 0x65: /* %gs: */
TRACE( "%04x/%04x at %p, fixing up\n", context->SegGs, system_gs, instr );
context->SegGs = system_gs;
return TRUE;
default:
return FALSE;
}
}
#include "pshpack1.h"
struct atl_thunk
@ -1716,6 +1757,8 @@ static void WINAPI raise_segv_exception( EXCEPTION_RECORD *rec, CONTEXT *context
{
if (rec->ExceptionInformation[0] == EXCEPTION_EXECUTE_FAULT && check_atl_thunk( rec, context ))
goto done;
if (rec->ExceptionInformation[1] == 0xffffffff && check_invalid_gs( context ))
goto done;
if (!(rec->ExceptionCode = virtual_handle_fault( (void *)rec->ExceptionInformation[1],
rec->ExceptionInformation[0] )))
goto done;