|author||Dave Hansen <firstname.lastname@example.org>||2015-01-08 14:30:20 -0800|
|committer||Thomas Gleixner <email@example.com>||2015-01-22 21:11:06 +0100|
x86, mpx: Explicitly disable 32-bit MPX support on 64-bit kernels
We had originally planned on submitting MPX support in one patch set. We eventually broke it up in to two pieces for easier review. One of the features that didn't make the first round was supporting 32-bit binaries on 64-bit kernels. Once we split the set up, we never added code to restrict 32-bit binaries from _using_ MPX on 64-bit kernels. The 32-bit bounds tables are a different format than the 64-bit ones. Without this patch, the kernel will try to read a 32-bit binary's tables as if they were the 64-bit version. They will likely be noticed as being invalid rather quickly and the app will get killed, but that's kinda mean. This patch adds an explicit check, and will make a 64-bit kernel essentially behave as if it has no MPX support when called from a 32-bit binary. Signed-off-by: Dave Hansen <firstname.lastname@example.org> Cc: Andy Lutomirski <email@example.com> Cc: Dave Hansen <firstname.lastname@example.org> Link: http://lkml.kernel.org/r/20150108223020.9E9AA511@viggo.jf.intel.com Signed-off-by: Thomas Gleixner <email@example.com>
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 67ebf575122..c439ec47821 100644
@@ -349,6 +349,12 @@ static __user void *task_get_bounds_dir(struct task_struct *tsk)
+ * 32-bit binaries on 64-bit kernels are currently
+ * unsupported.
+ if (IS_ENABLED(CONFIG_X86_64) && test_thread_flag(TIF_IA32))
+ return MPX_INVALID_BOUNDS_DIR;
* The bounds directory pointer is stored in a register
* only accessible if we first do an xsave.