[PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()

[PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

After commit 2736e8eeb0cc ("block: use the holder as indication for
exclusive opens"), blkdev_get_by_dev() will warn if holder is NULL and
mode contains 'FMODE_EXCL'.

holder from blkdev_get_by_dev() from disk_scan_partitions() is always NULL,
hence it should not use 'FMODE_EXCL', which is broben by the commit. For
consequence, WARN_ON_ONCE() will be triggered from blkdev_get_by_dev()
if user scan partitions with device opened exclusively.

Fix this problem by removing 'FMODE_EXCL' from disk_scan_partitions(),
as it used to be.

Reported-by: syzbot+00cd27751f78817f167b@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=00cd27751f78817f167b
Fixes: 2736e8eeb0cc ("block: use the holder as indication for exclusive opens")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/genhd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index 2c2f9a716822..1fb964866fd0 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -365,7 +365,8 @@ int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode)
 	}
 
 	set_bit(GD_NEED_PART_SCAN, &disk->state);
-	bdev = blkdev_get_by_dev(disk_devt(disk), mode, NULL, NULL);
+	bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
+				 NULL);
 	if (IS_ERR(bdev))
 		ret =  PTR_ERR(bdev);
 	else
-- 
2.39.2

Re: [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()

[kernel test robot]

Hi Yu,

kernel test robot noticed the following build errors:

[auto build test ERROR on next-20230616]

url:    https://github.com/intel-lab-lkp/linux/commits/Yu-Kuai/block-fix-wrong-mode-for-blkdev_get_by_dev-from-disk_scan_partitions/20230617-184451
base:   next-20230616
patch link:    https://lore.kernel.org/r/20230617103813.3708374-1-yukuai1%40huaweicloud.com
patch subject: [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()
config: alpha-randconfig-r036-20230617 (https://download.01.org/0day-ci/archive/20230617/202306172040.1dllc8rx-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 12.3.0
reproduce: (https://download.01.org/0day-ci/archive/20230617/202306172040.1dllc8rx-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202306172040.1dllc8rx-lkp@intel.com/

All errors (new ones prefixed by >>):

   block/genhd.c: In function 'disk_scan_partitions':
>> block/genhd.c:369:59: error: 'FMODE_EXCL' undeclared (first use in this function); did you mean 'FMODE_EXEC'?
     369 |         bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
         |                                                           ^~~~~~~~~~
         |                                                           FMODE_EXEC
   block/genhd.c:369:59: note: each undeclared identifier is reported only once for each function it appears in


vim +369 block/genhd.c

   342	
   343	int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode)
   344	{
   345		struct block_device *bdev;
   346		int ret = 0;
   347	
   348		if (disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN))
   349			return -EINVAL;
   350		if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
   351			return -EINVAL;
   352		if (disk->open_partitions)
   353			return -EBUSY;
   354	
   355		/*
   356		 * If the device is opened exclusively by current thread already, it's
   357		 * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
   358		 * synchronize with other exclusive openers and other partition
   359		 * scanners.
   360		 */
   361		if (!(mode & BLK_OPEN_EXCL)) {
   362			ret = bd_prepare_to_claim(disk->part0, disk_scan_partitions,
   363						  NULL);
   364			if (ret)
   365				return ret;
   366		}
   367	
   368		set_bit(GD_NEED_PART_SCAN, &disk->state);
 > 369		bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
   370					 NULL);
   371		if (IS_ERR(bdev))
   372			ret =  PTR_ERR(bdev);
   373		else
   374			blkdev_put(bdev, NULL);
   375	
   376		/*
   377		 * If blkdev_get_by_dev() failed early, GD_NEED_PART_SCAN is still set,
   378		 * and this will cause that re-assemble partitioned raid device will
   379		 * creat partition for underlying disk.
   380		 */
   381		clear_bit(GD_NEED_PART_SCAN, &disk->state);
   382		if (!(mode & BLK_OPEN_EXCL))
   383			bd_abort_claiming(disk->part0, disk_scan_partitions);
   384		return ret;
   385	}
   386	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()

[Yu Kuai]

Hi,

在 2023/06/17 20:25, kernel test robot 写道:
> 
>     block/genhd.c: In function 'disk_scan_partitions':
>>> block/genhd.c:369:59: error: 'FMODE_EXCL' undeclared (first use in this function); did you mean 'FMODE_EXEC'?
>       369 |         bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
>           |                                                           ^~~~~~~~~~
>           |                                                           FMODE_EXEC

Sorry about this typo, I'll send a new version.

Thanks,
Kuai

Re: [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()

[kernel test robot]

Hi Yu,

kernel test robot noticed the following build errors:

[auto build test ERROR on next-20230616]

url:    https://github.com/intel-lab-lkp/linux/commits/Yu-Kuai/block-fix-wrong-mode-for-blkdev_get_by_dev-from-disk_scan_partitions/20230617-184451
base:   next-20230616
patch link:    https://lore.kernel.org/r/20230617103813.3708374-1-yukuai1%40huaweicloud.com
patch subject: [PATCH -next] block: fix wrong mode for blkdev_get_by_dev() from disk_scan_partitions()
config: um-allnoconfig (https://download.01.org/0day-ci/archive/20230617/202306172025.taiLXERW-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
reproduce: (https://download.01.org/0day-ci/archive/20230617/202306172025.taiLXERW-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202306172025.taiLXERW-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from block/genhd.c:13:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/um/include/asm/hardirq.h:5:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     547 |         val = __raw_readb(PCI_IOBASE + addr);
         |                           ~~~~~~~~~~ ^
   include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     560 |         val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
      37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
         |                                                   ^
   In file included from block/genhd.c:13:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/um/include/asm/hardirq.h:5:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     573 |         val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
         |                                                         ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
      35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
         |                                                   ^
   In file included from block/genhd.c:13:
   In file included from include/linux/blkdev.h:9:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:12:
   In file included from include/linux/hardirq.h:11:
   In file included from arch/um/include/asm/hardirq.h:5:
   In file included from include/asm-generic/hardirq.h:17:
   In file included from include/linux/irq.h:20:
   In file included from include/linux/io.h:13:
   In file included from arch/um/include/asm/io.h:24:
   include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     584 |         __raw_writeb(value, PCI_IOBASE + addr);
         |                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     594 |         __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     604 |         __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
         |                                                       ~~~~~~~~~~ ^
   include/asm-generic/io.h:692:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     692 |         readsb(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:700:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     700 |         readsw(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:708:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     708 |         readsl(PCI_IOBASE + addr, buffer, count);
         |                ~~~~~~~~~~ ^
   include/asm-generic/io.h:717:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     717 |         writesb(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   include/asm-generic/io.h:726:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     726 |         writesw(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
   include/asm-generic/io.h:735:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
     735 |         writesl(PCI_IOBASE + addr, buffer, count);
         |                 ~~~~~~~~~~ ^
>> block/genhd.c:369:52: error: use of undeclared identifier 'FMODE_EXCL'
     369 |         bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
         |                                                           ^
   12 warnings and 1 error generated.


vim +/FMODE_EXCL +369 block/genhd.c

   342	
   343	int disk_scan_partitions(struct gendisk *disk, blk_mode_t mode)
   344	{
   345		struct block_device *bdev;
   346		int ret = 0;
   347	
   348		if (disk->flags & (GENHD_FL_NO_PART | GENHD_FL_HIDDEN))
   349			return -EINVAL;
   350		if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
   351			return -EINVAL;
   352		if (disk->open_partitions)
   353			return -EBUSY;
   354	
   355		/*
   356		 * If the device is opened exclusively by current thread already, it's
   357		 * safe to scan partitons, otherwise, use bd_prepare_to_claim() to
   358		 * synchronize with other exclusive openers and other partition
   359		 * scanners.
   360		 */
   361		if (!(mode & BLK_OPEN_EXCL)) {
   362			ret = bd_prepare_to_claim(disk->part0, disk_scan_partitions,
   363						  NULL);
   364			if (ret)
   365				return ret;
   366		}
   367	
   368		set_bit(GD_NEED_PART_SCAN, &disk->state);
 > 369		bdev = blkdev_get_by_dev(disk_devt(disk), mode & ~FMODE_EXCL, NULL,
   370					 NULL);
   371		if (IS_ERR(bdev))
   372			ret =  PTR_ERR(bdev);
   373		else
   374			blkdev_put(bdev, NULL);
   375	
   376		/*
   377		 * If blkdev_get_by_dev() failed early, GD_NEED_PART_SCAN is still set,
   378		 * and this will cause that re-assemble partitioned raid device will
   379		 * creat partition for underlying disk.
   380		 */
   381		clear_bit(GD_NEED_PART_SCAN, &disk->state);
   382		if (!(mode & BLK_OPEN_EXCL))
   383			bd_abort_claiming(disk->part0, disk_scan_partitions);
   384		return ret;
   385	}
   386	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki