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authorAndi Kleen <ak@suse.de>2006-04-07 19:50:00 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-09 11:53:52 -0700
commit7bf36bbc5e0c09271f9efe22162f8cc3f8ebd3d2 (patch)
tree9e97e2f5774824f0e2fbff1d4e7c49e9938285f5 /arch/x86_64
parent553f265fe883a23502ee351845f09334790f18b8 (diff)
[PATCH] x86_64: When user could have changed RIP always force IRET
Intel EM64T CPUs handle uncanonical return addresses differently from AMD CPUs. The exception is reported in the SYSRET, not the next instruction. This 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: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/x86_64')
-rw-r--r--arch/x86_64/kernel/entry.S12
1 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 10ec27b607f1..c946e4fe67a7 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
/*