The patch titled
Fix atomicity of TIF update in flush_thread() for powerpc
has been added to the -mm tree. Its filename is
fix-atomicity-of-tif-update-in-flush_thread-for-powerpc.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Fix atomicity of TIF update in flush_thread() for powerpc
From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
Fix atomicity of TIF update in flush_thread() for powerpc
Fixes it correctly with *_ti_thread_flag.
Race :
parent process executing :
sys_ptrace()
(lock_kernel())
(ptrace_get_task_struct(pid))
arch_ptrace()
ptrace_detach()
ptrace_disable(child);
clear_singlestep(child);
clear_tsk_thread_flag(child, TIF_SINGLESTEP);
(which clears the TIF_SINGLESTEP flag atomically from a different
process)
(put_task_struct(child))
(unlock_kernel())
And at the same time, in the child process :
sys_execve()
do_execve()
search_binary_handler()
load_elf_binary()
flush_old_exec()
flush_thread()
doing a non-atomic thread flag update
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
Acked-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/process.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff -puN arch/powerpc/kernel/process.c~fix-atomicity-of-tif-update-in-flush_thread-for-powerpc arch/powerpc/kernel/process.c
--- a/arch/powerpc/kernel/process.c~fix-atomicity-of-tif-update-in-flush_thread-for-powerpc
+++ a/arch/powerpc/kernel/process.c
@@ -465,8 +465,13 @@ void flush_thread(void)
#ifdef CONFIG_PPC64
struct thread_info *t = current_thread_info();
- if (t->flags & _TIF_ABI_PENDING)
- t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT);
+ if (test_ti_thread_flag(t, TIF_ABI_PENDING)) {
+ clear_ti_thread_flag(t, TIF_ABI_PENDING);
+ if (test_ti_thread_flag(t, TIF_32BIT))
+ clear_ti_thread_flag(t, TIF_32BIT);
+ else
+ set_ti_thread_flag(t, TIF_32BIT);
+ }
#endif
discard_lazy_cpu_state();
_
Patches currently in -mm which might be from mathieu.desnoyers@xxxxxxxxxx are
fix-atomicity-of-tif-update-in-flush_thread-for-powerpc.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-alpha.patch
atomich-complete-atomic_long-operations-in-asm-generic.patch
atomich-i386-type-safety-fix.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-ia64.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-mips.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-parisc.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-powerpc.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-sparc64.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-x86_64.patch
atomich-atomic_add_unless-as-inline-remove-systemh-atomich-circular-dependency.patch
local_t-architecture-independant-extension.patch
local_t-alpha-extension.patch
local_t-i386-extension.patch
local_t-ia64-extension.patch
local_t-mips-extension.patch
local_t-parisc-cleanup.patch
local_t-powerpc-extension.patch
local_t-sparc64-cleanup.patch
local_t-x86_64-extension.patch
linux-kernel-markers-kconfig-menus.patch
linux-kernel-markers-architecture-independant-code.patch
linux-kernel-markers-powerpc-optimization.patch
linux-kernel-markers-i386-optimization.patch
linux-kernel-markers-non-optimized-architectures.patch
linux-kernel-markers-documentation.patch
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