3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Mark Rutland mark.rutland@arm.com
commit c5bc503cbeee8586395aa541d2b53c69c3dd6930 upstream.
Our __die() implementation tries to dump the stack memory, in addition to a backtrace, which is problematic.
For contemporary 16K stacks, this can be a lot of data, which can take a long time to dump, and can push other useful context out of the kernel's printk ringbuffer (and/or a user's scrollback buffer on an attached console).
Additionally, the code implicitly assumes that the SP is on the task's stack, and tries to dump everything between the SP and the highest task stack address. When the SP points at an IRQ stack (or is corrupted), this makes the kernel attempt to dump vast amounts of VA space. With vmap'd stacks, this may result in erroneous accesses to peripherals.
This patch removes the memory dump, leaving us to rely on the backtrace, and other means of dumping stack memory such as kdump.
Signed-off-by: Mark Rutland mark.rutland@arm.com Reviewed-by: Will Deacon will.deacon@arm.com Tested-by: Laura Abbott labbott@redhat.com Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: James Morse james.morse@arm.com [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/arm64/kernel/traps.c | 2 -- 1 file changed, 2 deletions(-)
--- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -206,8 +206,6 @@ static int __die(const char *str, int er TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), thread + 1);
if (!user_mode(regs) || in_interrupt()) { - dump_mem(KERN_EMERG, "Stack: ", regs->sp, - THREAD_SIZE + (unsigned long)task_stack_page(tsk)); dump_backtrace(regs, tsk); dump_instr(KERN_EMERG, regs); }