| Message ID | 20180410023339.GB214542@rodete-desktop-imager.corp.google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Apr 10, 2018 at 11:33:39AM +0900, Minchan Kim wrote: > On Mon, Apr 09, 2018 at 06:12:11PM -0700, Matthew Wilcox wrote: > > On Tue, Apr 10, 2018 at 08:04:09AM +0900, Minchan Kim wrote: > > > On Mon, Apr 09, 2018 at 08:20:32AM -0700, Matthew Wilcox wrote: > > > > I don't think this is something the radix tree should know about. > > > > > > Because shadow entry implementation is hidden by radix tree implemetation. > > > IOW, radix tree user cannot know how it works. > > > > I have no idea what you mean. > > > > > > SLAB should be checking for it (the patch I posted earlier in this > > > > > > I don't think it's right approach. SLAB constructor can initialize > > > some metadata for slab page populated as well as page zeroing. > > > However, __GFP_ZERO means only clearing pages, not metadata. > > > So it's different semantic. No need to mix out. > > > > No, __GFP_ZERO is specified to clear the allocated memory whether > > you're allocating from alloc_pages or from slab. What makes no sense > > is allocating an object from slab with a constructor *and* __GFP_ZERO. > > They're in conflict, and slab can't fulfill both of those requirements. > > It's a stable material. If you really think it does make sense, > please submit patch separately. > > > > > > > thread), but the right place to filter this out is in the caller of > > > > radix_tree_maybe_preload -- it's already filtering out HIGHMEM pages, > > > > and should filter out GFP_ZERO too. > > > > > > radix_tree_[maybe]_preload is exported API, which are error-prone > > > for out of modules or upcoming customers. > > > > > > More proper place is __radix_tree_preload. > > > > I could not disagree with you more. It is the responsibility of the > > callers of radix_tree_preload to avoid calling it with nonsense flags > > like __GFP_DMA, __GFP_HIGHMEM or __GFP_ZERO. > > How about this? > > It would fix current problem and warn potential bugs as well. > radix_tree_preload already has done such warning and > radix_tree_maybe_preload has skipping for misbehaivor gfp. > > From 27ecf7a009d3570d1155c528c7f08040ede68ed3 Mon Sep 17 00:00:00 2001 > From: Minchan Kim <minchan@kernel.org> > Date: Tue, 10 Apr 2018 11:20:11 +0900 > Subject: [PATCH v2] mm: workingset: fix NULL ptr dereference > > It assumes shadow entries of radix tree rely on the init state > that node->private_list allocated newly is list_empty state > for the working. Currently, it's initailized in SLAB constructor > which means node of radix tree would be initialized only when > *slub allocates new page*, not *slub alloctes new object*. > > If some FS or subsystem pass gfp_mask to __GFP_ZERO, that means > newly allocated node can have !list_empty(node->private_list) > by memset of slab allocator. It ends up calling NULL deference > at workingset_update_node by failing list_empty check. > > This patch fixes it. > > Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check") > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Jan Kara <jack@suse.cz> > Cc: Matthew Wilcox <willy@infradead.org> > Cc: Jaegeuk Kim <jaegeuk@kernel.org> > Cc: Chao Yu <yuchao0@huawei.com> > Cc: Christopher Lameter <cl@linux.com> > Cc: linux-fsdevel@vger.kernel.org > Reported-by: Chris Fries <cfries@google.com> > Signed-off-by: Minchan Kim <minchan@kernel.org> > --- > lib/radix-tree.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/lib/radix-tree.c b/lib/radix-tree.c > index da9e10c827df..9d68f2a7888e 100644 > --- a/lib/radix-tree.c > +++ b/lib/radix-tree.c > @@ -511,6 +511,16 @@ int radix_tree_preload(gfp_t gfp_mask) > { > /* Warn on non-sensical use... */ > WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask)); > + /* > + * New allocate node must have node->private_list as INIT_LIST_HEAD > + * state by workingset shadow memory implementation. > + * If user pass __GFP_ZERO by mistake, slab allocator will clear > + * node->private_list, which makes a BUG. Rather than going Oops, > + * just fix and warn about it. > + */ > + if (WARN_ON(gfp_mask & __GFP_ZERO)) > + gfp_mask &= ~GFP_ZERO Build fail. If others are okay for this patch, I will resend fixed patch with stable mark. I will wait feedback from others. Thanks.
On Tue, Apr 10, 2018 at 11:33:39AM +0900, Minchan Kim wrote: > @@ -522,7 +532,7 @@ EXPORT_SYMBOL(radix_tree_preload); > */ > int radix_tree_maybe_preload(gfp_t gfp_mask) > { > - if (gfpflags_allow_blocking(gfp_mask)) > + if (gfpflags_allow_blocking(gfp_mask) && !(gfp_mask & __GFP_ZERO)) > return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); > /* Preloading doesn't help anything with this gfp mask, skip it */ > preempt_disable(); No, you've completely misunderstood what's going on in this function.
Hi Minchan,
I love your patch! Yet something to improve:
[auto build test ERROR on linus/master]
[also build test ERROR on v4.16 next-20180410]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Minchan-Kim/mm-workingset-fix-NULL-ptr-dereference/20180410-163500
config: x86_64-randconfig-x014-201814 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All error/warnings (new ones prefixed by >>):
lib/radix-tree.c: In function 'radix_tree_preload':
>> lib/radix-tree.c:522:16: error: 'GFP_ZERO' undeclared (first use in this function); did you mean '__GFP_ZERO'?
gfp_mask &= ~GFP_ZERO
^~~~~~~~
__GFP_ZERO
lib/radix-tree.c:522:16: note: each undeclared identifier is reported only once for each function it appears in
>> lib/radix-tree.c:524:2: error: expected ';' before 'return'
return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
^~~~~~
>> lib/radix-tree.c:525:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
vim +522 lib/radix-tree.c
500
501 /*
502 * Load up this CPU's radix_tree_node buffer with sufficient objects to
503 * ensure that the addition of a single element in the tree cannot fail. On
504 * success, return zero, with preemption disabled. On error, return -ENOMEM
505 * with preemption not disabled.
506 *
507 * To make use of this facility, the radix tree must be initialised without
508 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
509 */
510 int radix_tree_preload(gfp_t gfp_mask)
511 {
512 /* Warn on non-sensical use... */
513 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
514 /*
515 * New allocate node must have node->private_list as INIT_LIST_HEAD
516 * state by workingset shadow memory implementation.
517 * If user pass __GFP_ZERO by mistake, slab allocator will clear
518 * node->private_list, which makes a BUG. Rather than going Oops,
519 * just fix and warn about it.
520 */
521 if (WARN_ON(gfp_mask & __GFP_ZERO))
> 522 gfp_mask &= ~GFP_ZERO
523
> 524 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
> 525 }
526 EXPORT_SYMBOL(radix_tree_preload);
527
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
Hi Minchan,
I love your patch! Yet something to improve:
[auto build test ERROR on linus/master]
[also build test ERROR on v4.16 next-20180410]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
url: https://github.com/0day-ci/linux/commits/Minchan-Kim/mm-workingset-fix-NULL-ptr-dereference/20180410-163500
config: i386-randconfig-a0-201814 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
All errors (new ones prefixed by >>):
lib/radix-tree.c: In function 'radix_tree_preload':
>> lib/radix-tree.c:522:16: error: 'GFP_ZERO' undeclared (first use in this function)
gfp_mask &= ~GFP_ZERO
^
lib/radix-tree.c:522:16: note: each undeclared identifier is reported only once for each function it appears in
lib/radix-tree.c:524:2: error: expected ';' before 'return'
return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
^
lib/radix-tree.c:525:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
vim +/GFP_ZERO +522 lib/radix-tree.c
500
501 /*
502 * Load up this CPU's radix_tree_node buffer with sufficient objects to
503 * ensure that the addition of a single element in the tree cannot fail. On
504 * success, return zero, with preemption disabled. On error, return -ENOMEM
505 * with preemption not disabled.
506 *
507 * To make use of this facility, the radix tree must be initialised without
508 * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
509 */
510 int radix_tree_preload(gfp_t gfp_mask)
511 {
512 /* Warn on non-sensical use... */
513 WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
514 /*
515 * New allocate node must have node->private_list as INIT_LIST_HEAD
516 * state by workingset shadow memory implementation.
517 * If user pass __GFP_ZERO by mistake, slab allocator will clear
518 * node->private_list, which makes a BUG. Rather than going Oops,
519 * just fix and warn about it.
520 */
521 if (WARN_ON(gfp_mask & __GFP_ZERO))
> 522 gfp_mask &= ~GFP_ZERO
523
524 return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
525 }
526 EXPORT_SYMBOL(radix_tree_preload);
527
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
diff --git a/lib/radix-tree.c b/lib/radix-tree.c index da9e10c827df..9d68f2a7888e 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -511,6 +511,16 @@ int radix_tree_preload(gfp_t gfp_mask) { /* Warn on non-sensical use... */ WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask)); + /* + * New allocate node must have node->private_list as INIT_LIST_HEAD + * state by workingset shadow memory implementation. + * If user pass __GFP_ZERO by mistake, slab allocator will clear + * node->private_list, which makes a BUG. Rather than going Oops, + * just fix and warn about it. + */ + if (WARN_ON(gfp_mask & __GFP_ZERO)) + gfp_mask &= ~GFP_ZERO + return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); } EXPORT_SYMBOL(radix_tree_preload); @@ -522,7 +532,7 @@ EXPORT_SYMBOL(radix_tree_preload); */ int radix_tree_maybe_preload(gfp_t gfp_mask) { - if (gfpflags_allow_blocking(gfp_mask)) + if (gfpflags_allow_blocking(gfp_mask) && !(gfp_mask & __GFP_ZERO)) return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); /* Preloading doesn't help anything with this gfp mask, skip it */ preempt_disable();