The patch titled
mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix
has been added to the -mm tree. Its filename is
mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix.patch
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------------------------------------------------------
Subject: mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix
From: Michel Lespinasse <walken@xxxxxxxxxx>
On Sat, Dec 18, 2010 at 05:10:59AM -0500, Valdis.Kletnieks@xxxxxx wrote:
> On Thu, 16 Dec 2010 14:56:39 PST, akpm@xxxxxxxxxxxxxxxxxxxx said:
> > The mm-of-the-moment snapshot 2010-12-16-14-56 has been uploaded to
> >
> > http://userweb.kernel.org/~akpm/mmotm/
>
> The patch mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages.patch
> causes this chunk of code from cryptsetup-luks to fail during the initramfs:
>
> if (mlockall(MCL_CURRENT | MCL_FUTURE)) {
> log_err(ctx, _("WARNING!!! Possibly insecure memory. Are you root?\n"));
> _memlock_count--;
> return 0;
> }
>
> Bisection fingered this patch, which was added after -rc4-mmotm1202, which
> boots without tripping this log_err() call. I haven't tried building a
> -rc6-mmotm1216 with this patch reverted, because reverting it causes apply
> errors for subsequent patches.
>
> Ideas?
So I traced this down using valdis's initramfs image. This is actually
an interesting corner case:
Some VMA has the VM_MAY_(READ/WRITE/EXEC) flags, but is currently protected
with PROT_NONE permissions (VM_READ/WRITE_EXEC flags are all cleared).
When mlockall() is called, the old code would see mlock_fixup() return
an error for that VMA, which would be ignored by do_mlockall(). The new
code did not ignore errors from do_mlock_pages(), which broke backwards
compatibility.
So the trivial fix to make mlockall behave identically as before could be
as follows:
Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Valdis Kletnieks <Valdis.Kletnieks@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/mlock.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff -puN mm/mlock.c~mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix mm/mlock.c
--- a/mm/mlock.c~mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix
+++ a/mm/mlock.c
@@ -476,7 +476,7 @@ static int do_mlock(unsigned long start,
return error;
}
-static int do_mlock_pages(unsigned long start, size_t len)
+static int do_mlock_pages(unsigned long start, size_t len, int ignore_errors)
{
struct mm_struct *mm = current->mm;
unsigned long end, nstart, nend;
@@ -513,6 +513,10 @@ static int do_mlock_pages(unsigned long
*/
if (vma->vm_flags & VM_LOCKED) {
ret = __mlock_vma_pages_range(vma, nstart, nend);
+ if (ret < 0 && ignore_errors) {
+ ret = 0;
+ continue; /* continue at next VMA */
+ }
if (ret) {
ret = __mlock_posix_error_return(ret);
break;
@@ -550,7 +554,7 @@ SYSCALL_DEFINE2(mlock, unsigned long, st
error = do_mlock(start, len, 1);
up_write(¤t->mm->mmap_sem);
if (!error)
- error = do_mlock_pages(start, len);
+ error = do_mlock_pages(start, len, 0);
return error;
}
@@ -615,8 +619,10 @@ SYSCALL_DEFINE1(mlockall, int, flags)
capable(CAP_IPC_LOCK))
ret = do_mlockall(flags);
up_write(¤t->mm->mmap_sem);
- if (!ret && (flags & MCL_CURRENT))
- ret = do_mlock_pages(0, TASK_SIZE);
+ if (!ret && (flags & MCL_CURRENT)) {
+ /* Ignore errors */
+ do_mlock_pages(0, TASK_SIZE, 1);
+ }
out:
return ret;
}
_
Patches currently in -mm which might be from walken@xxxxxxxxxx are
do_wp_page-remove-the-reuse-flag.patch
do_wp_page-clarify-dirty_page-handling.patch
mlock-avoid-dirtying-pages-and-triggering-writeback.patch
mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages.patch
mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix.patch
mm-add-foll_mlock-follow_page-flag.patch
mm-move-vm_locked-check-to-__mlock_vma_pages_range.patch
mlock-do-not-hold-mmap_sem-for-extended-periods-of-time.patch
mlock-do-not-hold-mmap_sem-for-extended-periods-of-time-fix.patch
mlock-do-not-hold-mmap_sem-for-extended-periods-of-time-fix2.patch
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