diff options
| author | Dianzhang Chen <dianzhangchen0@gmail.com> | 2019-06-26 12:50:30 +0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2019-10-31 22:14:59 +0000 |
| commit | 8c53bd9834261151c0c68f3164cf5cc6f7a965af (patch) | |
| tree | dd2b20e799b43a11ea169db53b12e5f3a70034ae /arch | |
| parent | 58ba5001051390e30d726fc44240ed182aa26c1b (diff) | |
x86/tls: Fix possible spectre-v1 in do_get_thread_area()
commit 993773d11d45c90cb1c6481c2638c3d9f092ea5b upstream.
The index to access the threads tls array is controlled by userspace
via syscall: sys_ptrace(), hence leading to a potential exploitation
of the Spectre variant 1 vulnerability.
The index can be controlled from:
ptrace -> arch_ptrace -> do_get_thread_area.
Fix this by sanitizing the user supplied index before using it to access
the p->thread.tls_array.
Signed-off-by: Dianzhang Chen <dianzhangchen0@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: bp@alien8.de
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/1561524630-3642-1-git-send-email-dianzhangchen0@gmail.com
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/tls.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c index 7fc5e843f247..9f03c7e07a2b 100644 --- a/arch/x86/kernel/tls.c +++ b/arch/x86/kernel/tls.c @@ -4,6 +4,7 @@ #include <linux/user.h> #include <linux/regset.h> #include <linux/syscalls.h> +#include <linux/nospec.h> #include <asm/uaccess.h> #include <asm/desc.h> @@ -177,6 +178,7 @@ int do_get_thread_area(struct task_struct *p, int idx, struct user_desc __user *u_info) { struct user_desc info; + int index; if (idx == -1 && get_user(idx, &u_info->entry_number)) return -EFAULT; @@ -184,8 +186,11 @@ int do_get_thread_area(struct task_struct *p, int idx, if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX) return -EINVAL; - fill_user_desc(&info, idx, - &p->thread.tls_array[idx - GDT_ENTRY_TLS_MIN]); + index = idx - GDT_ENTRY_TLS_MIN; + index = array_index_nospec(index, + GDT_ENTRY_TLS_MAX - GDT_ENTRY_TLS_MIN + 1); + + fill_user_desc(&info, idx, &p->thread.tls_array[index]); if (copy_to_user(u_info, &info, sizeof(info))) return -EFAULT; |