This is a note to let you know that I've just added the patch titled arm64: backtrace: Don't bother trying to unwind the userspace stack to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm64-backtrace-don-t-bother-trying-to-unwind-the-userspace-stack.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 1e6f5440a6814d28c32d347f338bfef68bc3e69d Mon Sep 17 00:00:00 2001 From: Will Deacon <will.deacon@xxxxxxx> Date: Mon, 8 Apr 2019 17:56:34 +0100 Subject: arm64: backtrace: Don't bother trying to unwind the userspace stack From: Will Deacon <will.deacon@xxxxxxx> commit 1e6f5440a6814d28c32d347f338bfef68bc3e69d upstream. Calling dump_backtrace() with a pt_regs argument corresponding to userspace doesn't make any sense and our unwinder will simply print "Call trace:" before unwinding the stack looking for user frames. Rather than go through this song and dance, just return early if we're passed a user register state. Cc: <stable@xxxxxxxxxxxxxxx> Fixes: 1149aad10b1e ("arm64: Add dump_backtrace() in show_regs") Reported-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Signed-off-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/traps.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -101,10 +101,16 @@ static void dump_instr(const char *lvl, void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame; - int skip; + int skip = 0; pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); + if (regs) { + if (user_mode(regs)) + return; + skip = 1; + } + if (!tsk) tsk = current; @@ -125,7 +131,6 @@ void dump_backtrace(struct pt_regs *regs frame.graph = tsk->curr_ret_stack; #endif - skip = !!regs; printk("Call trace:\n"); do { /* skip until specified stack frame */ @@ -175,15 +180,13 @@ static int __die(const char *str, int er return ret; print_modules(); - __show_regs(regs); pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n", TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), end_of_stack(tsk)); + show_regs(regs); - if (!user_mode(regs)) { - dump_backtrace(regs, tsk); + if (!user_mode(regs)) dump_instr(KERN_EMERG, regs); - } return ret; } Patches currently in stable-queue which might be from will.deacon@xxxxxxx are queue-4.19/arm64-futex-fix-futex_wake_op-atomic-ops-with-non-zero-result-value.patch queue-4.19/arm64-kaslr-reserve-size-of-arm64_memstart_align-in-.patch queue-4.19/arm64-backtrace-don-t-bother-trying-to-unwind-the-userspace-stack.patch