lkml.org 
[lkml]   [2016]   [May]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] x86/mm: Switch from TASK_SIZE to TASK_SIZE_MAX in the page fault code
Date
x86's page fault handlers had two TASK_SIZE uses that should have
been TASK_SIZE_MAX. I don't think that either one had a visible
effect, but this makes the code clearer and should save a few bytes
of text.

(And I eventually want to eradicate TASK_SIZE. This will help.)

Reported-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/mm/fault.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 1d75b98a8414..45940239b983 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -292,7 +292,7 @@ void vmalloc_sync_all(void)
return;

for (address = VMALLOC_START & PMD_MASK;
- address >= TASK_SIZE && address < FIXADDR_TOP;
+ address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
address += PMD_SIZE) {
struct page *page;

@@ -854,8 +854,13 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
return;
}
#endif
- /* Kernel addresses are always protection faults: */
- if (address >= TASK_SIZE)
+
+ /*
+ * To avoid leaking information about the kernel page table
+ * layout, pretend that user-mode accesses to kernel addresses
+ * are always protection faults.
+ */
+ if (address >= TASK_SIZE_MAX)
error_code |= PF_PROT;

if (likely(show_unhandled_signals))
--
2.5.5
\
 
 \ /
  Last update: 2016-05-10 23:41    [W:0.399 / U:0.208 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site