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Subject[PATCH 16/41] arm64: sanitize compat_ptrace_write_user()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

don't bother with copy_regset_from_user() (not to mention
set_fs())

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/arm64/kernel/ptrace.c | 29 ++++++++++++++++++++---------
1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index d5f3da5197a1..9f769e862f68 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1553,8 +1553,8 @@ static int compat_ptrace_read_user(struct task_struct *tsk, compat_ulong_t off,
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();
+ struct pt_regs newregs = *task_pt_regs(tsk);
+ unsigned int idx = off / 4;

if (off & 3 || off >= COMPAT_USER_SZ)
return -EIO;
@@ -1562,14 +1562,25 @@ 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);
+ switch (idx) {
+ case 15:
+ newregs.pc = val;
+ break;
+ case 16:
+ newregs.pstate = compat_psr_to_pstate(val);
+ break;
+ case 17:
+ newregs.orig_x0 = val;
+ break;
+ default:
+ newregs.regs[idx] = val;
+ }
+
+ if (!valid_user_regs(&newregs.user_regs, tsk))
+ return -EINVAL;

- return ret;
+ *task_pt_regs(tsk) = newregs;
+ return 0;
}

#ifdef CONFIG_HAVE_HW_BREAKPOINT
--
2.11.0
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