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authorWill Deacon <will.deacon@arm.com>2014-06-02 11:47:23 +0100
committerMark Brown <broonie@linaro.org>2014-07-23 00:02:12 +0100
commitab7ccd91004b55c29910c999f51bc40880646810 (patch)
tree05b730cd37515f410ac6d038ca91ff031f097323
parent039f36de814fba40f6aa8359fd0948d48f36dd68 (diff)
downloadlinux-linaro-stable-ab7ccd91004b55c29910c999f51bc40880646810.tar.gz
arm64: ptrace: change fs when passing kernel pointer to regset code
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.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 5341534b6d04..85536688f753 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -872,6 +872,7 @@ 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;
@@ -879,10 +880,13 @@ 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;
}