[PATCH AUTOSEL 4.9 29/90] mm: pagewalk: fix termination condition in walk_pte_range()

[PATCH AUTOSEL 4.9 29/90] mm: pagewalk: fix termination condition in walk_pte_range()

[Sasha Levin]

From: Steven Price <steven.price@arm.com>

[ Upstream commit c02a98753e0a36ba65a05818626fa6adeb4e7c97 ]

If walk_pte_range() is called with a 'end' argument that is beyond the
last page of memory (e.g.  ~0UL) then the comparison between 'addr' and
'end' will always fail and the loop will be infinite.  Instead change the
comparison to >= while accounting for overflow.

Link: http://lkml.kernel.org/r/20191218162402.45610-15-steven.price@arm.com
Signed-off-by: Steven Price <steven.price@arm.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zong Li <zong.li@sifive.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/pagewalk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index d95341cffc2f6..8d6290502631a 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -14,9 +14,9 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
 		if (err)
 		       break;
-		addr += PAGE_SIZE;
-		if (addr == end)
+		if (addr >= end - PAGE_SIZE)
 			break;
+		addr += PAGE_SIZE;
 		pte++;
 	}
 
-- 
2.25.1

[PATCH AUTOSEL 4.9 62/90] mm/filemap.c: clear page error before actual read

[Sasha Levin]

From: Xianting Tian <xianting_tian@126.com>

[ Upstream commit faffdfa04fa11ccf048cebdde73db41ede0679e0 ]

Mount failure issue happens under the scenario: Application forked dozens
of threads to mount the same number of cramfs images separately in docker,
but several mounts failed with high probability.  Mount failed due to the
checking result of the page(read from the superblock of loop dev) is not
uptodate after wait_on_page_locked(page) returned in function cramfs_read:

   wait_on_page_locked(page);
   if (!PageUptodate(page)) {
      ...
   }

The reason of the checking result of the page not uptodate: systemd-udevd
read the loopX dev before mount, because the status of loopX is Lo_unbound
at this time, so loop_make_request directly trigger the calling of io_end
handler end_buffer_async_read, which called SetPageError(page).  So It
caused the page can't be set to uptodate in function
end_buffer_async_read:

   if(page_uptodate && !PageError(page)) {
      SetPageUptodate(page);
   }

Then mount operation is performed, it used the same page which is just
accessed by systemd-udevd above, Because this page is not uptodate, it
will launch a actual read via submit_bh, then wait on this page by calling
wait_on_page_locked(page).  When the I/O of the page done, io_end handler
end_buffer_async_read is called, because no one cleared the page
error(during the whole read path of mount), which is caused by
systemd-udevd reading, so this page is still in "PageError" status, which
can't be set to uptodate in function end_buffer_async_read, then caused
mount failure.

But sometimes mount succeed even through systemd-udeved read loopX dev
just before, The reason is systemd-udevd launched other loopX read just
between step 3.1 and 3.2, the steps as below:

1, loopX dev default status is Lo_unbound;
2, systemd-udved read loopX dev (page is set to PageError);
3, mount operation
   1) set loopX status to Lo_bound;
   ==>systemd-udevd read loopX dev<==
   2) read loopX dev(page has no error)
   3) mount succeed

As the loopX dev status is set to Lo_bound after step 3.1, so the other
loopX dev read by systemd-udevd will go through the whole I/O stack, part
of the call trace as below:

   SYS_read
      vfs_read
          do_sync_read
              blkdev_aio_read
                 generic_file_aio_read
                     do_generic_file_read:
                        ClearPageError(page);
                        mapping->a_ops->readpage(filp, page);

here, mapping->a_ops->readpage() is blkdev_readpage.  In latest kernel,
some function name changed, the call trace as below:

   blkdev_read_iter
      generic_file_read_iter
         generic_file_buffered_read:
            /*
             * A previous I/O error may have been due to temporary
             * failures, eg. mutipath errors.
             * Pg_error will be set again if readpage fails.
             */
            ClearPageError(page);
            /* Start the actual read. The read will unlock the page*/
            error=mapping->a_ops->readpage(flip, page);

We can see ClearPageError(page) is called before the actual read,
then the read in step 3.2 succeed.

This patch is to add the calling of ClearPageError just before the actual
read of read path of cramfs mount.  Without the patch, the call trace as
below when performing cramfs mount:

   do_mount
      cramfs_read
         cramfs_blkdev_read
            read_cache_page
               do_read_cache_page:
                  filler(data, page);
                  or
                  mapping->a_ops->readpage(data, page);

With the patch, the call trace as below when performing mount:

   do_mount
      cramfs_read
         cramfs_blkdev_read
            read_cache_page:
               do_read_cache_page:
                  ClearPageError(page); <== new add
                  filler(data, page);
                  or
                  mapping->a_ops->readpage(data, page);

With the patch, mount operation trigger the calling of
ClearPageError(page) before the actual read, the page has no error if no
additional page error happen when I/O done.

Signed-off-by: Xianting Tian <xianting_tian@126.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: <yubin@h3c.com>
Link: http://lkml.kernel.org/r/1583318844-22971-1-git-send-email-xianting_tian@126.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/filemap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index b046d8f147e20..05af91f495f53 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2474,6 +2474,14 @@ filler:
 		unlock_page(page);
 		goto out;
 	}
+
+	/*
+	 * A previous I/O error may have been due to temporary
+	 * failures.
+	 * Clear page error before actual read, PG_error will be
+	 * set again if read page fails.
+	 */
+	ClearPageError(page);
 	goto filler;
 
 out:
-- 
2.25.1

[PATCH AUTOSEL 4.9 63/90] mm/mmap.c: initialize align_offset explicitly for vm_unmapped_area

[Sasha Levin]

From: Jaewon Kim <jaewon31.kim@samsung.com>

[ Upstream commit 09ef5283fd96ac424ef0e569626f359bf9ab86c9 ]

On passing requirement to vm_unmapped_area, arch_get_unmapped_area and
arch_get_unmapped_area_topdown did not set align_offset.  Internally on
both unmapped_area and unmapped_area_topdown, if info->align_mask is 0,
then info->align_offset was meaningless.

But commit df529cabb7a2 ("mm: mmap: add trace point of
vm_unmapped_area") always prints info->align_offset even though it is
uninitialized.

Fix this uninitialized value issue by setting it to 0 explicitly.

Before:
  vm_unmapped_area: addr=0x755b155000 err=0 total_vm=0x15aaf0 flags=0x1 len=0x109000 lo=0x8000 hi=0x75eed48000 mask=0x0 ofs=0x4022

After:
  vm_unmapped_area: addr=0x74a4ca1000 err=0 total_vm=0x168ab1 flags=0x1 len=0x9000 lo=0x8000 hi=0x753d94b000 mask=0x0 ofs=0x0

Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20200409094035.19457-1-jaewon31.kim@samsung.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/mmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 7109f886e739e..7c8815636c482 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2028,6 +2028,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
 	info.low_limit = mm->mmap_base;
 	info.high_limit = TASK_SIZE;
 	info.align_mask = 0;
+	info.align_offset = 0;
 	return vm_unmapped_area(&info);
 }
 #endif
@@ -2069,6 +2070,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 	info.high_limit = mm->mmap_base;
 	info.align_mask = 0;
+	info.align_offset = 0;
 	addr = vm_unmapped_area(&info);
 
 	/*
-- 
2.25.1