diff options
author | Will Deacon <will.deacon@arm.com> | 2014-06-02 11:47:23 +0100 |
---|---|---|
committer | Mark Brown <broonie@linaro.org> | 2014-07-23 00:02:44 +0100 |
commit | c94bbb52ec7e667b597cc528a44382f859921b29 (patch) | |
tree | dc63e61c4604f1589dfcdbb315aee91537ce00dd | |
parent | 455c6fdbd219161bd09b1165f11699d6d73de11c (diff) |
arm64: ptrace: change fs when passing kernel pointer to regset codev3.14/topic/arm64-ptrace
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@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit c168870704bcde6bb63d05f7882b620dd3985a46)
Signed-off-by: Mark Brown <broonie@linaro.org>
-rw-r--r-- | arch/arm64/kernel/ptrace.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 6a8928bba03c..bf288e443a9f 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -821,6 +821,7 @@ 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; @@ -828,10 +829,13 @@ 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; } |