diff options
| author | Andi Kleen <ak@suse.de> | 2006-04-12 08:19:29 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2006-04-12 13:06:54 -0700 |
| commit | 6b12095a4a0e1f21bbf83f95f13299ca99d758fe (patch) | |
| tree | 5d2a3d96f7b99a3a225c0f7a110c6631848524b0 | |
| parent | 59b2832a31ae2f3279bb5b16ae9b1c4e38e40dea (diff) | |
[PATCH] x86_64: When user could have changed RIP always force IRET (CVE-2006-0744)
Intel EM64T CPUs handle uncanonical return addresses differently from
AMD CPUs.
The exception is reported in the SYSRET, not the next instruction.
Thgis leads to the kernel exception handler running on the user stack
with the wrong GS because the kernel didn't expect exceptions on this
instruction.
This version of the patch has the teething problems that plagued an
earlier version fixed.
This is CVE-2006-0744
Thanks to Ernie Petrides and Asit B. Mallick for analysis and initial
patches.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | arch/x86_64/kernel/entry.S | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S index 25dcb775559..ab6e44dcd1e 100644 --- a/arch/x86_64/kernel/entry.S +++ b/arch/x86_64/kernel/entry.S @@ -180,6 +180,10 @@ rff_trace: * * XXX if we had a free scratch register we could save the RSP into the stack frame * and report it properly in ps. Unfortunately we haven't. + * + * When user can change the frames always force IRET. That is because + * it deals with uncanonical addresses better. SYSRET has trouble + * with them due to bugs in both AMD and Intel CPUs. */ ENTRY(system_call) @@ -254,7 +258,10 @@ sysret_signal: xorl %esi,%esi # oldset -> arg2 call ptregscall_common 1: movl $_TIF_NEED_RESCHED,%edi - jmp sysret_check + /* Use IRET because user could have changed frame. This + works because ptregscall_common has called FIXUP_TOP_OF_STACK. */ + cli + jmp int_with_check badsys: movq $-ENOSYS,RAX-ARGOFFSET(%rsp) @@ -280,7 +287,8 @@ tracesys: call syscall_trace_leave RESTORE_TOP_OF_STACK %rbx RESTORE_REST - jmp ret_from_sys_call + /* Use IRET because user could have changed frame */ + jmp int_ret_from_sys_call CFI_ENDPROC /* |