This is a note to let you know that I've just added the patch titled
x86/compat: Simplify compat syscall userspace allocation
to the 5.10-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:
x86-compat-simplify-compat-syscall-userspace-allocat.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 48a9fc8b13722c354335c399cd8de298acb5b0df
Author: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Date: Sat Oct 3 23:25:28 2020 -0400
x86/compat: Simplify compat syscall userspace allocation
[ Upstream commit 214f0e804358cdd13b5cbe4445189f23e30618b4 ]
When allocating user memory space for a compat system call, don't consider
whether the originating code is IA32 or X32, just allocate from a safe
region for both, beyond the redzone. This should be safe for IA32, and has
the benefit of avoiding TIF_IA32, which is about to be removed.
Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20201004032536.1229030-3-krisman@xxxxxxxxxxxxx
Stable-dep-of: 7fea700e04bd ("zap_pid_ns_processes: clear TIF_NOTIFY_SIGNAL along with TIF_SIGPENDING")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index 46a067bd7e0ba..8f7af1f890406 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -175,14 +175,13 @@ typedef struct user_regs_struct compat_elf_gregset_t;
static inline void __user *arch_compat_alloc_user_space(long len)
{
- compat_uptr_t sp;
-
- if (test_thread_flag(TIF_IA32)) {
- sp = task_pt_regs(current)->sp;
- } else {
- /* -128 for the x32 ABI redzone */
- sp = task_pt_regs(current)->sp - 128;
- }
+ compat_uptr_t sp = task_pt_regs(current)->sp;
+
+ /*
+ * -128 for the x32 ABI redzone. For IA32, it is not strictly
+ * necessary, but not harmful.
+ */
+ sp -= 128;
return (void __user *)round_down(sp - len, 16);
}
