Messages in this thread Patch in this message | | | From | Mark Rutland <> | Subject | [PATCH v2 9/9] x86: snapshot thread flags | Date | Mon, 21 Jun 2021 10:06:02 +0100 |
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Some thread flags can be set remotely, and so even when IRQs are disabled, the flags can change under our feet. Generally this is unlikely to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race.
To avoid such issues, a snapshot of the flags has to be taken prior to using them. Some places already use READ_ONCE() for that, others do not.
Convert them all to the new flag accessor helpers.
Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Ingo Molnar <mingo@redhat.com> --- arch/x86/kernel/process.c | 8 ++++---- arch/x86/kernel/process.h | 6 +++--- arch/x86/mm/tlb.c | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 5e1f38179f49..d1c4a93c6e26 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -332,7 +332,7 @@ void arch_setup_new_exec(void) clear_thread_flag(TIF_SSBD); task_clear_spec_ssb_disable(current); task_clear_spec_ssb_noexec(current); - speculation_ctrl_update(task_thread_info(current)->flags); + speculation_ctrl_update(read_thread_flags()); } } @@ -584,7 +584,7 @@ static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk) clear_tsk_thread_flag(tsk, TIF_SPEC_IB); } /* Return the updated threadinfo flags*/ - return task_thread_info(tsk)->flags; + return read_task_thread_flags(tsk); } void speculation_ctrl_update(unsigned long tif) @@ -620,8 +620,8 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p) { unsigned long tifp, tifn; - tifn = READ_ONCE(task_thread_info(next_p)->flags); - tifp = READ_ONCE(task_thread_info(prev_p)->flags); + tifn = read_task_thread_flags(next_p); + tifp = read_task_thread_flags(prev_p); switch_to_bitmap(tifp); diff --git a/arch/x86/kernel/process.h b/arch/x86/kernel/process.h index 1d0797b2338a..0b1be8685b49 100644 --- a/arch/x86/kernel/process.h +++ b/arch/x86/kernel/process.h @@ -13,9 +13,9 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p); static inline void switch_to_extra(struct task_struct *prev, struct task_struct *next) { - unsigned long next_tif = task_thread_info(next)->flags; - unsigned long prev_tif = task_thread_info(prev)->flags; - + unsigned long next_tif = read_task_thread_flags(next); + unsigned long prev_tif = read_task_thread_flags(prev); + if (IS_ENABLED(CONFIG_SMP)) { /* * Avoid __switch_to_xtra() invocation when conditional diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 78804680e923..fcc5e22050d4 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -318,7 +318,7 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next, static unsigned long mm_mangle_tif_spec_ib(struct task_struct *next) { - unsigned long next_tif = task_thread_info(next)->flags; + unsigned long next_tif = read_task_thread_flags(next); unsigned long ibpb = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_IBPB; return (unsigned long)next->mm | ibpb; -- 2.11.0
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