[3.11.y.z extended stable] Patch "arm64: ptrace: change fs when passing kernel pointer to regset code" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Tue Jul 1 08:51:22 UTC 2014
This is a note to let you know that I have just added a patch titled
arm64: ptrace: change fs when passing kernel pointer to regset code
to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From 9a6b29211d27b0e0fdb08205b545a1f8896a9281 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon at arm.com>
Date: Mon, 2 Jun 2014 11:47:23 +0100
Subject: arm64: ptrace: change fs when passing kernel pointer to regset code
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 at arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
arch/arm64/kernel/ptrace.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index c484d5625ffb..9fa78cd0f092 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -823,6 +823,7 @@ static int compat_ptrace_write_user(struct task_struct *tsk, compat_ulong_t off,
compat_ulong_t val)
{
int ret;
+ mm_segment_t old_fs = get_fs();
if (off & 3 || off >= COMPAT_USER_SZ)
return -EIO;
@@ -830,10 +831,13 @@ static int compat_ptrace_write_user(struct task_struct *tsk, compat_ulong_t off,
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;
}
--
1.9.1
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