We cannot restart cacheflush safely if a process provides user-defined signal handler and signal is pending. In this case -EINTR is returned and it is expected that process re-invokes syscall. However, there are a few problems with that: * looks like nobody bothers checking return value from cacheflush * but if it did, we don't provide the restart address for that, so the process has to use the same range again * ...and again, what might lead to looping forever So, remove cacheflush restarting code and terminate cache flushing as early as fatal signal is pending. Cc: stable@xxxxxxxxxxxxxxx # 3.12+ Reported-by: Chanho Min <chanho.min@xxxxxxx> Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx> Acked-by: Will Deacon <will.deacon@xxxxxxx> --- Hi, There is my proposal for the problem reported in [1]. Since that thread has not been progressing much, I'm addressing the problem in separate patch. Comments? [1] https://lkml.org/lkml/2014/11/13/29 arch/arm/include/asm/thread_info.h | 11 ----------- arch/arm/kernel/traps.c | 31 ++----------------------------- 2 files changed, 2 insertions(+), 40 deletions(-) diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index fc44d37..ce73ab6 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -44,16 +44,6 @@ struct cpu_context_save { __u32 extra[2]; /* Xscale 'acc' register, etc */ }; -struct arm_restart_block { - union { - /* For user cache flushing */ - struct { - unsigned long start; - unsigned long end; - } cache; - }; -}; - /* * low level task data that entry.S needs immediate access to. * __switch_to() assumes cpu_context follows immediately after cpu_domain. @@ -79,7 +69,6 @@ struct thread_info { unsigned long thumbee_state; /* ThumbEE Handler Base register */ #endif struct restart_block restart_block; - struct arm_restart_block arm_restart_block; }; #define INIT_THREAD_INFO(tsk) \ diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index 0c8b108..8dd03ee 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -533,8 +533,6 @@ static int bad_syscall(int n, struct pt_regs *regs) return regs->ARM_r0; } -static long do_cache_op_restart(struct restart_block *); - static inline int __do_cache_op(unsigned long start, unsigned long end) { @@ -543,24 +541,8 @@ __do_cache_op(unsigned long start, unsigned long end) do { unsigned long chunk = min(PAGE_SIZE, end - start); - if (signal_pending(current)) { - struct thread_info *ti = current_thread_info(); - - ti->restart_block = (struct restart_block) { - .fn = do_cache_op_restart, - }; - - ti->arm_restart_block = (struct arm_restart_block) { - { - .cache = { - .start = start, - .end = end, - }, - }, - }; - - return -ERESTART_RESTARTBLOCK; - } + if (fatal_signal_pending(current)) + return 0; ret = flush_cache_user_range(start, start + chunk); if (ret) @@ -573,15 +555,6 @@ __do_cache_op(unsigned long start, unsigned long end) return 0; } -static long do_cache_op_restart(struct restart_block *unused) -{ - struct arm_restart_block *restart_block; - - restart_block = ¤t_thread_info()->arm_restart_block; - return __do_cache_op(restart_block->cache.start, - restart_block->cache.end); -} - static inline int do_cache_op(unsigned long start, unsigned long end, int flags) { -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html