Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200728163416.556521-1-hch@lst.de> <20200728163416.556521-3-hch@lst.de>
In-Reply-To: <20200728163416.556521-3-hch@lst.de>
From:   Naresh Kamboju <naresh.kamboju@linaro.org>
Date:   Thu, 6 Aug 2020 20:14:48 +0530
Message-ID: <CA+G9fYuYxGBKR5aQqCQwA=SjLRDbyQKwQYJvbJRaKT7qwy7voQ@mail.gmail.com>
Subject: Re: [PATCH 02/23] fs: refactor ksys_umount
To:     Christoph Hellwig <hch@lst.de>
Cc:     Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        open list <linux-kernel@vger.kernel.org>,
        linux-raid@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-api@vger.kernel.org, Jan Stancek <jstancek@redhat.com>,
        chrubis <chrubis@suse.cz>, lkft-triage@lists.linaro.org,
        LTP List <ltp@lists.linux.it>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, 28 Jul 2020 at 22:04, Christoph Hellwig <hch@lst.de> wrote:
>
> Factor out a path_umount helper that takes a struct path * instead of the
> actual file name.  This will allow to convert the init and devtmpfs code
> to properly mount based on a kernel pointer instead of relying on the
> implicit set_fs(KERNEL_DS) during early init.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/namespace.c | 40 ++++++++++++++++++----------------------
>  1 file changed, 18 insertions(+), 22 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 6f8234f74bed90..43834b59eff6c3 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -1706,36 +1706,19 @@ static inline bool may_mandlock(void)
>  }
>  #endif
>
> -/*
> - * Now umount can handle mount points as well as block devices.
> - * This is important for filesystems which use unnamed block devices.
> - *
> - * We now support a flag for forced unmount like the other 'big iron'
> - * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
> - */
> -
> -int ksys_umount(char __user *name, int flags)
> +static int path_umount(struct path *path, int flags)
>  {
> -       struct path path;
>         struct mount *mnt;
>         int retval;
> -       int lookup_flags = LOOKUP_MOUNTPOINT;
>
>         if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
>                 return -EINVAL;
> -
>         if (!may_mount())
>                 return -EPERM;
>
> -       if (!(flags & UMOUNT_NOFOLLOW))
> -               lookup_flags |= LOOKUP_FOLLOW;
> -
> -       retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
> -       if (retval)
> -               goto out;
> -       mnt = real_mount(path.mnt);
> +       mnt = real_mount(path->mnt);
>         retval = -EINVAL;
> -       if (path.dentry != path.mnt->mnt_root)
> +       if (path->dentry != path->mnt->mnt_root)
>                 goto dput_and_out;
>         if (!check_mnt(mnt))
>                 goto dput_and_out;
> @@ -1748,12 +1731,25 @@ int ksys_umount(char __user *name, int flags)
>         retval = do_umount(mnt, flags);
>  dput_and_out:
>         /* we mustn't call path_put() as that would clear mnt_expiry_mark */
> -       dput(path.dentry);
> +       dput(path->dentry);
>         mntput_no_expire(mnt);
> -out:
>         return retval;
>  }
>
> +int ksys_umount(char __user *name, int flags)
> +{
> +       int lookup_flags = LOOKUP_MOUNTPOINT;
> +       struct path path;
> +       int ret;
> +
> +       if (!(flags & UMOUNT_NOFOLLOW))
> +               lookup_flags |= LOOKUP_FOLLOW;
> +       ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
> +       if (ret)
> +               return ret;
> +       return path_umount(&path, flags);
> +}
> +
>  SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
>  {
>         return ksys_umount(name, flags);

Regressions on linux next 20200803 tag kernel.
LTP syscalls test umount03 mount a path for testing and
umount failed and retired for 50 times and test exit with warning
and following test cases using that mount path failed.

LTP syscalls tests failed list,
    * umount03
    * umount2_01
    * umount2_02
    * umount2_03
    * utime06
    * copy_file_range01


Summary
------------------------------------------------------------------------

kernel: 5.8.0
git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
git branch: master
git describe: next-20200803
Test details: https://qa-reports.linaro.org/lkft/linux-next-oe/build/next-20200803
------------------------------------------------------------------------

test failed log:
tst_device.c:262: INFO: Using test device LTP_DEV='/dev/loop0'
tst_mkfs.c:90: INFO: Formatting /dev/loop0 with ext2 opts='' extra opts=''
mke2fs 1.43.8 (1-Jan-2018)
tst_test.c:1246: INFO: Timeout per run is 0h 15m 00s
[  870.449934] EXT4-fs (loop0): mounting ext2 file system using the
ext4 subsystem
[  870.454338] EXT4-fs (loop0): mounted filesystem without journal. Opts: (null)
[  870.456412] ext2 filesystem being mounted at
/tmp/ltp-YQrzWZNEEy/jVhqum/mntpoint supports timestamps until 2038
(0x7fffffff)
umount03.c:35: PASS: umount() fails as expected: EPERM (1)
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  1...
tst_device.c:388: INFO: Likely gvfsd-trash is probing newly mounted
fs, kill it to speed up tests.
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  2...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  3...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  4...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  5...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  6...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  7...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  8...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try  9...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 10...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 11...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 12...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 13...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 14...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 15...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 16...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 17...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 18...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 19...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 20...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 21...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 22...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 23...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 24...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 25...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 26...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 27...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 28...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 29...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 30...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 31...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 32...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 33...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 34...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 35...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 36...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 37...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 38...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 39...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 40...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 41...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 42...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 43...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 44...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 45...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 46...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 47...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 48...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 49...
tst_device.c:384: INFO: umount('mntpoint') failed with EBUSY, try 50...
tst_device.c:394: WARN: Failed to umount('mntpoint') after 50 retries
tst_tmpdir.c:337: WARN: tst_rmdir: rmobj(/tmp/ltp-YQrzWZNEEy/jVhqum)
failed: remove(/tmp/ltp-YQrzWZNEEy/jVhqum/mntpoint) failed; errno=16:
EBUSY
Summary:
passed   1
failed   0
skipped  0
warnings 1

mke2fs 1.43.8 (1-Jan-2018)
/dev/loop0 is mounted; will not make a filesystem here!
umount2_01    0  TINFO  :  Using test device LTP_DEV='/dev/loop0'
umount2_01    0  TINFO  :  Formatting /dev/loop0 with ext2 opts='' extra opts=''
umount2_01    1  TBROK  :  tst_mkfs.c:103: umount2_01.c:81: mkfs.ext2
failed with 1
umount2_01    2  TBROK  :  tst_mkfs.c:103: Remaining cases broken
mke2fs 1.43.8 (1-Jan-2018)
/dev/loop0 is mounted; will not make a filesystem here!
umount2_02    0  TINFO  :  Using test device LTP_DEV='/dev/loop0'
umount2_02    0  TINFO  :  Formatting /dev/loop0 with ext2 opts='' extra opts=''
umount2_02    1  TBROK  :  tst_mkfs.c:103: umount2_02.c:121: mkfs.ext2
failed with 1
umount2_02    2  TBROK  :  tst_mkfs.c:103: Remaining cases broken
mke2fs 1.43.8 (1-Jan-2018)
/dev/loop0 is mounted; will not make a filesystem here!
umount2_03    0  TINFO  :  Using test device LTP_DEV='/dev/loop0'
umount2_03    0  TINFO  :  Formatting /dev/loop0 with ext2 opts='' extra opts=''
umount2_03    1  TBROK  :  tst_mkfs.c:103: umount2_03.c:101: mkfs.ext2
failed with 1
umount2_03    2  TBROK  :  tst_mkfs.c:103: Remaining cases broken

mke2fs 1.43.8 (1-Jan-2018)
/dev/loop0 is mounted; will not make a filesystem here!
utime06     0  TINFO  :  Using test device LTP_DEV='/dev/loop0'
utime06     0  TINFO  :  Formatting /dev/loop0 with ext2 opts='' extra opts=''
utime06     1  TBROK  :  tst_mkfs.c:103: utime06.c:122: mkfs.ext2 failed with 1
utime06     2  TBROK  :  tst_mkfs.c:103: Remaining cases broken

Steps to reproduce:
-------------------------
cd /opt/ltp
./runltp -s umount                 --> FAILS

Above command runs all umount tests.

Test case description,
Verify that umount(2) returns -1 and sets errno to EPERM if the user
is not the super-user.
Test case link,
https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/umount/umount03.c

full test log,
https://lkft.validation.linaro.org/scheduler/job/1642287

--
Linaro LKFT
https://lkft.linaro.org