Commit-ID: b81ff1013eb8eef2934ca7e8cf53d553c1029e84
Gitweb: https://git.kernel.org/tip/b81ff1013eb8eef2934ca7e8cf53d553c1029e84
Author: Hugh Dickins <[email protected]>
AuthorDate: Wed, 29 May 2019 09:25:40 +0200
Committer: Borislav Petkov <[email protected]>
CommitDate: Thu, 6 Jun 2019 19:15:17 +0200
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/[email protected]
Fixes: d9c9ce34ed5c8 ("x86/fpu: Fault-in user stack if
copy_fpstate_to_sigframe() fails")
Suggested-by: Andrew Morton <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Tested-by: Chris Wilson <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: linux-mm <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Link:
https://lkml.kernel.org/r/[email protected]
---
arch/x86/kernel/fpu/signal.c | 11 ++---------
1 file 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;
}
