From: Jeff Xu <jef...@google.com>
mprotect(2) changes protection of VMAs in the given address
range. Sealing will prevent unintended mprotect call.
What this patch does:
When a mprotect(2) is invoked, if one of its VMAs has MM_SEAL_MPROTECT
set from previous mseal(2) call, this mprotect(2) will fail, without
any VMA modified.
This patch is based on following:
1. do_mprotect_pkey() currently called in two places:
SYSCALL_DEFINE3(mprotect,...)
SYSCALL_DEFINE4(pkey_mprotect, ...)
and not in any other places, therefore omit changing the signature of
do_mprotect_pkey(), i.e. not passing checkSeals flag.
2. In do_mprotect_pkey(), calls can_modify_mm() before any
update is made on the VMAs.
Signed-off-by: Jeff Xu <jef...@google.com>
---
mm/mprotect.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 130db91d3a8c..6321c4d0aa3f 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -32,6 +32,7 @@
#include <linux/sched/sysctl.h>
#include <linux/userfaultfd_k.h>
#include <linux/memory-tiers.h>
+#include <uapi/linux/mman.h>
#include <asm/cacheflush.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
@@ -753,6 +754,20 @@ static int do_mprotect_pkey(unsigned long start, size_t
len,
}
}
+ /*
+ * do_mprotect_pkey() currently called from two places:
+ * SYSCALL_DEFINE3(mprotect,...)
+ * SYSCALL_DEFINE4(pkey_mprotect, ...)
+ * and not from other places.
+ * Therefore, omit changing the signature of do_mprotect_pkey().
+ * Otherwise, we might need to add checkSeals and pass it
+ * from all callers of do_mprotect_pkey().
+ */
+ if (!can_modify_mm(current->mm, start, end, MM_SEAL_MPROTECT)) {
+ error = -EACCES;
+ goto out;
+ }
+
prev = vma_prev(&vmi);
if (start > vma->vm_start)
prev = vma;
--
2.42.0.655.g421f12c284-goog
