aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorNadav Amit <[email protected]>2019-04-25 17:11:30 -0700
committerIngo Molnar <[email protected]>2019-04-30 12:37:54 +0200
commit7298e24f904224fa79eb8fd7e0fbd78950ccf2db (patch)
treea018e0a4c2a38810c9a52cbcfdfd986e8052bf36
parent3c0dab44e22782359a0a706cbce72de99a22aa75 (diff)
x86/kprobes: Set instruction page as executable
Set the page as executable after allocation. This patch is a preparatory patch for a following patch that makes module allocated pages non-executable. While at it, do some small cleanup of what appears to be unnecessary masking. Signed-off-by: Nadav Amit <[email protected]> Signed-off-by: Rick Edgecombe <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
-rw-r--r--arch/x86/kernel/kprobes/core.c24
1 files changed, 20 insertions, 4 deletions
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index fed46ddb1eef..06058c44ab57 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -431,8 +431,20 @@ void *alloc_insn_page(void)
void *page;
page = module_alloc(PAGE_SIZE);
- if (page)
- set_memory_ro((unsigned long)page & PAGE_MASK, 1);
+ if (!page)
+ return NULL;
+
+ /*
+ * First make the page read-only, and only then make it executable to
+ * prevent it from being W+X in between.
+ */
+ set_memory_ro((unsigned long)page, 1);
+
+ /*
+ * TODO: Once additional kernel code protection mechanisms are set, ensure
+ * that the page was not maliciously altered and it is still zeroed.
+ */
+ set_memory_x((unsigned long)page, 1);
return page;
}
@@ -440,8 +452,12 @@ void *alloc_insn_page(void)
/* Recover page to RW mode before releasing it */
void free_insn_page(void *page)
{
- set_memory_nx((unsigned long)page & PAGE_MASK, 1);
- set_memory_rw((unsigned long)page & PAGE_MASK, 1);
+ /*
+ * First make the page non-executable, and only then make it writable to
+ * prevent it from being W+X in between.
+ */
+ set_memory_nx((unsigned long)page, 1);
+ set_memory_rw((unsigned long)page, 1);
module_memfree(page);
}