summaryrefslogtreecommitdiff
path: root/arch/x86
diff options
context:
space:
mode:
authorHugh Dickins <hughd@google.com>2019-05-29 09:25:40 +0200
committerBorislav Petkov <bp@suse.de>2019-06-06 19:15:17 +0200
commitb81ff1013eb8eef2934ca7e8cf53d553c1029e84 (patch)
tree0bda9a0f7ebb0793213ba2932d843a83bef84482 /arch/x86
parente35faeb64146f2015f2aec14b358ae508e4066db (diff)
x86/fpu: Use fault_in_pages_writeable() for pre-faulting
Since commit d9c9ce34ed5c8 ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails") get_user_pages_unlocked() pre-faults user's memory if a write generates a page fault while the handler is disabled. This works in general and uncovered a bug as reported by Mike Rapoport¹. It has been pointed out that this function may be fragile and a simple pre-fault as in fault_in_pages_writeable() would be a better solution. Better as in taste and simplicity: that write (as performed by the alternative function) performs exactly the same faulting of memory as before. This was suggested by Hugh Dickins and Andrew Morton. Use fault_in_pages_writeable() for pre-faulting user's stack. [ bigeasy: Write commit message. ] [ bp: Massage some. ] ¹ https://lkml.kernel.org/r/1557844195-18882-1-git-send-email-rppt@linux.ibm.com Fixes: d9c9ce34ed5c8 ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails") Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: linux-mm <linux-mm@kvack.org> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190529072540.g46j4kfeae37a3iu@linutronix.de Link: https://lkml.kernel.org/r/1557844195-18882-1-git-send-email-rppt@linux.ibm.com
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/fpu/signal.c11
1 files changed, 2 insertions, 9 deletions
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 5a8d118bc423..060d6188b453 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -5,6 +5,7 @@
#include <linux/compat.h>
#include <linux/cpu.h>
+#include <linux/pagemap.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
@@ -189,15 +190,7 @@ retry:
fpregs_unlock();
if (ret) {
- int aligned_size;
- int nr_pages;
-
- aligned_size = offset_in_page(buf_fx) + fpu_user_xstate_size;
- nr_pages = DIV_ROUND_UP(aligned_size, PAGE_SIZE);
-
- ret = get_user_pages_unlocked((unsigned long)buf_fx, nr_pages,
- NULL, FOLL_WRITE);
- if (ret == nr_pages)
+ if (!fault_in_pages_writeable(buf_fx, fpu_user_xstate_size))
goto retry;
return -EFAULT;
}