+ zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch added to -mm tree

+ zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch added to -mm tree

[akpm]

The patch titled
     Subject: zram: pass down the bvec we need to read into in the work struct
has been added to the -mm tree.  Its filename is
     zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Jérôme Glisse <jglisse@redhat.com>
Subject: zram: pass down the bvec we need to read into in the work struct

When scheduling work item to read page we need to pass down the proper
bvec struct which points to the page to read into.  Before this patch it
uses a randomly initialized bvec (only if PAGE_SIZE != 4096) which is
wrong.

Note that without this patch on arch/kernel where PAGE_SIZE != 4096
userspace could read random memory through a zram block device (thought
userspace probably would have no control on the address being read).

Link: http://lkml.kernel.org/r/20190408183219.26377-1-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/block/zram/zram_drv.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/block/zram/zram_drv.c~zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct
+++ a/drivers/block/zram/zram_drv.c
@@ -774,18 +774,18 @@ struct zram_work {
 	struct zram *zram;
 	unsigned long entry;
 	struct bio *bio;
+	struct bio_vec bvec;
 };
 
 #if PAGE_SIZE != 4096
 static void zram_sync_read(struct work_struct *work)
 {
-	struct bio_vec bvec;
 	struct zram_work *zw = container_of(work, struct zram_work, work);
 	struct zram *zram = zw->zram;
 	unsigned long entry = zw->entry;
 	struct bio *bio = zw->bio;
 
-	read_from_bdev_async(zram, &bvec, entry, bio);
+	read_from_bdev_async(zram, &zw->bvec, entry, bio);
 }
 
 /*
@@ -798,6 +798,7 @@ static int read_from_bdev_sync(struct zr
 {
 	struct zram_work work;
 
+	work.bvec = *bvec;
 	work.zram = zram;
 	work.entry = entry;
 	work.bio = bio;
_

Patches currently in -mm which might be from jglisse@redhat.com are

zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch
mm-hmm-select-mmu-notifier-when-selecting-hmm-v2.patch
mm-hmm-use-reference-counting-for-hmm-struct-v3.patch
mm-hmm-do-not-erase-snapshot-when-a-range-is-invalidated.patch
mm-hmm-improve-and-rename-hmm_vma_get_pfns-to-hmm_range_snapshot-v2.patch
mm-hmm-improve-and-rename-hmm_vma_fault-to-hmm_range_fault-v3.patch
mm-hmm-improve-driver-api-to-work-and-wait-over-a-range-v3.patch
mm-hmm-add-default-fault-flags-to-avoid-the-need-to-pre-fill-pfns-arrays-v2.patch
mm-hmm-mirror-hugetlbfs-snapshoting-faulting-and-dma-mapping-v3.patch
mm-hmm-allow-to-mirror-vma-of-a-file-on-a-dax-backed-filesystem-v3.patch
mm-hmm-add-helpers-to-test-if-mm-is-still-alive-or-not.patch
mm-hmm-add-an-helper-function-that-fault-pages-and-map-them-to-a-device-v3.patch
mm-hmm-add-an-helper-function-that-fault-pages-and-map-them-to-a-device-v3-fix.patch
mm-hmm-convert-various-hmm_pfn_-to-device_entry-which-is-a-better-name.patch
mm-mmu_notifier-helper-to-test-if-a-range-invalidation-is-blockable.patch
mm-mmu_notifier-convert-user-range-blockable-to-helper-function.patch
mm-mmu_notifier-convert-mmu_notifier_range-blockable-to-a-flags.patch
mm-mmu_notifier-contextual-information-for-event-enums.patch
mm-mmu_notifier-contextual-information-for-event-triggering-invalidation-v2.patch
mm-mmu_notifier-use-correct-mmu_notifier-events-for-each-invalidation.patch
mm-mmu_notifier-pass-down-vma-and-reasons-why-mmu-notifier-is-happening-v2.patch
mm-mmu_notifier-mmu_notifier_range_update_to_read_only-helper.patch

Re: + zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch added to -mm tree

[Minchan Kim]

On Tue, Apr 16, 2019 at 04:53:50PM -0700, akpm@linux-foundation.org wrote:
> 
> The patch titled
>      Subject: zram: pass down the bvec we need to read into in the work struct
> has been added to the -mm tree.  Its filename is
>      zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch
> 
> This patch should soon appear at
>     http://ozlabs.org/~akpm/mmots/broken-out/zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch
> and later at
>     http://ozlabs.org/~akpm/mmotm/broken-out/zram-pass-down-the-bvec-we-need-to-read-into-in-the-work-struct.patch
> 
> Before you just go and hit "reply", please:
>    a) Consider who else should be cc'ed
>    b) Prefer to cc a suitable mailing list as well
>    c) Ideally: find the original patch on the mailing list and do a
>       reply-to-all to that, adding suitable additional cc's
> 
> *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
> 
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
> 
> ------------------------------------------------------
> From: Jérôme Glisse <jglisse@redhat.com>
> Subject: zram: pass down the bvec we need to read into in the work struct
> 
> When scheduling work item to read page we need to pass down the proper
> bvec struct which points to the page to read into.  Before this patch it
> uses a randomly initialized bvec (only if PAGE_SIZE != 4096) which is
> wrong.
> 
> Note that without this patch on arch/kernel where PAGE_SIZE != 4096
> userspace could read random memory through a zram block device (thought
> userspace probably would have no control on the address being read).
> 
> Link: http://lkml.kernel.org/r/20190408183219.26377-1-jglisse@redhat.com
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Nitin Gupta <ngupta@vflare.org>
> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Thanks for the nice catch, Jerome!
That sync/async read code in zram is really mess. :(

Acked-by: Minchan Kim <minchan@kernel.org>