This is a note to let you know that I've just added the patch titled
arm64: don't call break hooks for BRK exceptions from EL0
to the 3.16-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-don-t-call-break-hooks-for-brk-exceptions-from-el0.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c878e0cff5c5e56b216951cbe75f7a3dd500a736 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@xxxxxxx>
Date: Thu, 31 Jul 2014 11:36:08 +0100
Subject: arm64: don't call break hooks for BRK exceptions from EL0
From: Will Deacon <will.deacon@xxxxxxx>
commit c878e0cff5c5e56b216951cbe75f7a3dd500a736 upstream.
Our break hooks are used to handle brk exceptions from kgdb (and potentially
kprobes if that code ever resurfaces), so don't bother calling them if
the BRK exception comes from userspace.
This prevents userspace from trapping to a kdb shell on systems where
kgdb is enabled and active.
Reported-by: Omar Sandoval <osandov@xxxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/debug-monitors.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -315,20 +315,20 @@ static int brk_handler(unsigned long add
{
siginfo_t info;
- if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
- return 0;
+ if (user_mode(regs)) {
+ info = (siginfo_t) {
+ .si_signo = SIGTRAP,
+ .si_errno = 0,
+ .si_code = TRAP_BRKPT,
+ .si_addr = (void __user *)instruction_pointer(regs),
+ };
- if (!user_mode(regs))
+ force_sig_info(SIGTRAP, &info, current);
+ } else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
+ pr_warning("Unexpected kernel BRK exception at EL1\n");
return -EFAULT;
+ }
- info = (siginfo_t) {
- .si_signo = SIGTRAP,
- .si_errno = 0,
- .si_code = TRAP_BRKPT,
- .si_addr = (void __user *)instruction_pointer(regs),
- };
-
- force_sig_info(SIGTRAP, &info, current);
return 0;
}
Patches currently in stable-queue which might be from will.deacon@xxxxxxx are
queue-3.16/arm64-don-t-call-break-hooks-for-brk-exceptions-from-el0.patch
queue-3.16/arm64-fix-barriers-used-for-page-table-modifications.patch
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