diff options
author | Hugh Dickins <hughd@google.com> | 2019-05-29 09:25:40 +0200 |
---|---|---|
committer | Borislav Petkov <bp@suse.de> | 2019-06-06 19:15:17 +0200 |
commit | b81ff1013eb8eef2934ca7e8cf53d553c1029e84 (patch) | |
tree | 0bda9a0f7ebb0793213ba2932d843a83bef84482 /arch/x86/kernel/fpu | |
parent | e35faeb64146f2015f2aec14b358ae508e4066db (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/kernel/fpu')
-rw-r--r-- | arch/x86/kernel/fpu/signal.c | 11 |
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; } |