[v18,17/25] x86/mpx: pass @mm to kernel_managing_mpx_tables() in mpx_notify_unmap()

Commit Message

Jarkko Sakkinen Dec. 21, 2018, 11:11 p.m. UTC

If @mm is not the same as current->mm, mpx_notify_unmap() will yield
invalid results and at worst will lead to a crash if it gets called by a
kthread.

The function in question gets called through do_munmap(). ATM kernel does
not use that function on x86 in such context that mm and current->mm would
differ

With the addition of SGX driver code, do_munmap() is called from workqueue
thread. This commit changes the parameter passed to @mm so that this will
yield the correct results and not crash as reference to current->mm would
be NULL in a kthread context.

Cc: Dave Hansen <[e-mail]>
Fixes: 1de4fa14ee25 ("x86, mpx: Cleanup unused bound tables")
Signed-off-by: Jarkko Sakkinen <[e-mail]>
---
 arch/x86/mm/mpx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 2385538e8065..15fb62657ee9 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -882,7 +882,7 @@  static int mpx_unmap_tables(struct mm_struct *mm,
  * necessary, and the 'vma' is the first vma in this range (start -> end).
  */
 void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
-		unsigned long start, unsigned long end)
+		      unsigned long start, unsigned long end)
 {
 	int ret;
 
@@ -890,7 +890,7 @@  void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * Refuse to do anything unless userspace has asked
 	 * the kernel to help manage the bounds tables,
 	 */
-	if (!kernel_managing_mpx_tables(current->mm))
+	if (!kernel_managing_mpx_tables(mm))
 		return;
 	/*
 	 * This will look across the entire 'start -> end' range,