The following commit has been merged into the core/entry branch of tip: Commit-ID: 5796ee48d26a18930a8b86fb865ba195282889d0 Gitweb: https://git.kernel.org/tip/5796ee48d26a18930a8b86fb865ba195282889d0 Author: Mark Rutland <mark.rutland@xxxxxxx> AuthorDate: Wed, 17 Nov 2021 16:30:49 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Fri, 26 Nov 2021 21:20:14 +01:00 x86: Snapshot thread flags 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@xxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Link: https://lore.kernel.org/r/20211117163050.53986-12-mark.rutland@xxxxxxx --- arch/x86/kernel/process.c | 8 ++++---- arch/x86/kernel/process.h | 4 ++-- arch/x86/mm/tlb.c | 2 +- 3 files changed, 7 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 04143a6..5d48103 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -365,7 +365,7 @@ 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()); } } @@ -617,7 +617,7 @@ 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) @@ -653,8 +653,8 @@ 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 1d0797b..76b547b 100644 --- a/arch/x86/kernel/process.h +++ b/arch/x86/kernel/process.h @@ -13,8 +13,8 @@ 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)) { /* diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 59ba296..92bb03b 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -361,7 +361,7 @@ static void l1d_flush_evaluate(unsigned long prev_mm, unsigned long next_mm, static unsigned long mm_mangle_tif_spec_bits(struct task_struct *next) { - unsigned long next_tif = task_thread_info(next)->flags; + unsigned long next_tif = read_task_thread_flags(next); unsigned long spec_bits = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_SPEC_MASK; /*
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