This is a note to let you know that I've just added the patch titled
arm64: ptrace: change fs when passing kernel pointer to regset code
to the 3.15-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-ptrace-change-fs-when-passing-kernel-pointer-to-regset-code.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c168870704bcde6bb63d05f7882b620dd3985a46 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@xxxxxxx>
Date: Mon, 2 Jun 2014 11:47:23 +0100
Subject: arm64: ptrace: change fs when passing kernel pointer to regset code
From: Will Deacon <will.deacon@xxxxxxx>
commit c168870704bcde6bb63d05f7882b620dd3985a46 upstream.
Our compat PTRACE_POKEUSR implementation simply passes the user data to
regset_copy_from_user after some simple range checking. Unfortunately,
the data in question has already been copied to the kernel stack by this
point, so the subsequent access_ok check fails and the ptrace request
returns -EFAULT. This causes problems tracing fork() with older versions
of strace.
This patch briefly changes the fs to KERNEL_DS, so that the access_ok
check passes even with a kernel address.
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/ptrace.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -821,6 +821,7 @@ static int compat_ptrace_write_user(stru
compat_ulong_t val)
{
int ret;
+ mm_segment_t old_fs = get_fs();
if (off & 3 || off >= COMPAT_USER_SZ)
return -EIO;
@@ -828,10 +829,13 @@ static int compat_ptrace_write_user(stru
if (off >= sizeof(compat_elf_gregset_t))
return 0;
+ set_fs(KERNEL_DS);
ret = copy_regset_from_user(tsk, &user_aarch32_view,
REGSET_COMPAT_GPR, off,
sizeof(compat_ulong_t),
&val);
+ set_fs(old_fs);
+
return ret;
}
Patches currently in stable-queue which might be from will.deacon@xxxxxxx are
queue-3.15/arm64-ptrace-change-fs-when-passing-kernel-pointer-to-regset-code.patch
queue-3.15/arm64-ptrace-fix-empty-registers-set-in-prstatus-of-aarch32-process-core.patch
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