x32: make sure TS_COMPAT is cleared for x32 tasks

PATCH In review Bobby Powers 2 participants 3 messages Feb 26, 2012 x86

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Bobby Powers

author

2012-02-26 04:25 UTC #0 lore raw

PATCH 1/1 x32: make sure TS_COMPAT is cleared for x32 tasks

If a process has a non-x32 ia32 personality and changes to x32, the process would keep its TS_COMPAT flag. x32 uses the presence of the x32 flag on a syscall to determine compat status, so make sure TS_COMPAT is cleared.

Signed-off-by Bobby Powers <[email protected]>

---
 arch/x86/kernel/process_64.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

arch/x86/kernel/process_64.c +3 -0

index e9ec8f1..a465973 100644
@@ -539,6 +539,9 @@ void set_personality_ia32(bool x32)
 		clear_thread_flag(TIF_IA32);
 		set_thread_flag(TIF_X32);
 		current->personality &= ~READ_IMPLIES_EXEC;
+		/* is_compat_task() uses the presence of the x32
+		   syscall bit flag to determine compat status */
+		current_thread_info()->status &= ~TS_COMPAT;
 	} else {
 		set_thread_flag(TIF_IA32);
 		clear_thread_flag(TIF_X32);

Signature · 1 line

1.7.7.6

tip-bot for Bobby Powers

author

2012-02-26 05:51 UTC #1 lore raw

[tip:x86/x32] x32: Make sure TS_COMPAT is cleared for x32 tasks

Commit-ID:  ce5f7a99df87918b5be4618a9386213a8e9a7146
Gitweb:     http://git.kernel.org/tip/ce5f7a99df87918b5be4618a9386213a8e9a7146
Author:     Bobby Powers <[email protected]>
AuthorDate: Sat, 25 Feb 2012 23:25:38 -0500
Committer:  H. Peter Anvin <[email protected]>
CommitDate: Sat, 25 Feb 2012 20:42:18 -0800

x32: Make sure TS_COMPAT is cleared for x32 tasks

Signed-off-by Bobby Powers <[email protected]>

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by H. Peter Anvin <[email protected]>

---
 arch/x86/kernel/process_64.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

arch/x86/kernel/process_64.c +3 -0

index a0701da..32e0412 100644
@@ -540,6 +540,9 @@ void set_personality_ia32(bool x32)
 		clear_thread_flag(TIF_IA32);
 		set_thread_flag(TIF_X32);
 		current->personality &= ~READ_IMPLIES_EXEC;
+		/* is_compat_task() uses the presence of the x32
+		   syscall bit flag to determine compat status */
+		current_thread_info()->status &= ~TS_COMPAT;
 	} else {
 		set_thread_flag(TIF_IA32);
 		clear_thread_flag(TIF_X32);

H. Peter Anvin

reviewer

2012-02-26 05:55 UTC #2 lore raw

In reply to Bobby Powers

Quoted 15 lines · Bobby Powers

If a process has a non-x32 ia32 personality and changes to x32, the process would keep its TS_COMPAT flag. x32 uses the presence of the x32 flag on a syscall to determine compat status, so make sure TS_COMPAT is cleared.
Signed-off-by Bobby Powers <[email protected]>
---
 arch/x86/kernel/process_64.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
arch/x86/kernel/process_64.c +0 -0
index e9ec8f1..a465973 100644

arch/x86/kernel/process_64.c void set_personality_ia32(bool x32) · line 547

Quoted 9 lines

arch/x86/kernel/process_64.c +3 -0

@@ -539,6 +539,9 @@ void set_personality_ia32(bool x32)
 		clear_thread_flag(TIF_IA32);
 		set_thread_flag(TIF_X32);
 		current->personality &= ~READ_IMPLIES_EXEC;
+		/* is_compat_task() uses the presence of the x32
+		   syscall bit flag to determine compat status */
+		current_thread_info()->status &= ~TS_COMPAT;
 	} else {
 		set_thread_flag(TIF_IA32);
 		clear_thread_flag(TIF_X32);

I suspect we should also clear TS_COMPAT in set_personality_64() ... this is not x32-related, but would affect the behavior when execing a 64-bit task from an i386 compatibility task. I have no idea if it actually makes any difference, and clearly it can't have been too broken since noone has found a problem all these years, but it looks wrong...

-hpa

Signature · 2 lines

H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.