[PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

[PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

[zhanchengbin]

If there is a tmpfs with the same name as the disk, and mount before the 
disk,example:
	/dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
	/dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0

Create a hard link /dev/sdd-ln for the disk and resize2fs it.The items in
/proc/mounts are traversed, When you get to tmpfs,file!=mnt->mnt_fsname,
Therefore, the stat(mnt->mnt_fsname, &st_buf) branch is used,However, the
values of file_rdev and st_buf.st_rdev are the same.As a result, the system
mistakenly considers that disk is mounted to /root/tmp.As a result,resize2fs
fails.

mkdir /root/tmp
mkdir /root/mnt
mkfs.ext4 -F -b 1024 -E "resize=10000000" /dev/sdd 32768
mount -t tmpfs /dev/sdd /root/tmp
mount /dev/sdd /root/mnt
ln /dev/sdd /dev/sdd-ln
resize2fs /dev/sdd-ln 6G

Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
Signed-off-by: guiyao@huawei.com
---
  lib/ext2fs/ismounted.c | 9 +++++++--
  1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index aee7d726..463a82a6 100644
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -98,6 +98,7 @@ static errcode_t check_mntent_file(const char 
*mtab_file, const char *file,
  {
  	struct mntent 	*mnt;
  	struct stat	st_buf;
+	struct stat	dir_st_buf;
  	errcode_t	retval = 0;
  	dev_t		file_dev=0, file_rdev=0;
  	ino_t		file_ino=0;
@@ -144,8 +145,12 @@ static errcode_t check_mntent_file(const char 
*mtab_file, const char *file,
  		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
  			if (ext2fsP_is_disk_device(st_buf.st_mode)) {
  #ifndef __GNU__
-				if (file_rdev && (file_rdev == st_buf.st_rdev))
-					break;
+				if (file_rdev && (file_rdev == st_buf.st_rdev)) {
+					if (stat(mnt->mnt_dir, &dir_st_buf) != 0)
+						continue;
+					if (file_rdev == dir_st_buf.st_dev)
+						break;
+				}
  				if (check_loop_mounted(mnt->mnt_fsname,
  						st_buf.st_rdev, file_dev,
  						file_ino) == 1)
-- 
2.23.0

Re: [PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

[zhanchengbin]

If there is a tmpfs with the same name as the disk, and mount before the 
disk,example:
	/dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
	/dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0

Create a hard link /dev/sdd-ln for the disk and resize2fs it.The items in
/proc/mounts are traversed, When you get to tmpfs,file!=mnt->mnt_fsname,
Therefore, the stat(mnt->mnt_fsname, &st_buf) branch is used,However, the
values of file_rdev and st_buf.st_rdev are the same.As a result, the system
mistakenly considers that disk is mounted to /root/tmp.As a result,resize2fs
fails.

mkdir /root/tmp
mkdir /root/mnt
mkfs.ext4 -F -b 1024 -E "resize=10000000" /dev/sdd 32768
mount -t tmpfs /dev/sdd /root/tmp
mount /dev/sdd /root/mnt
ln /dev/sdd /dev/sdd-ln
resize2fs /dev/sdd-ln 6G

Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
Signed-off-by: guiyao <guiyao@huawei.com>
---
  lib/ext2fs/ismounted.c | 9 +++++++--
  1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
index aee7d726..463a82a6 100644
--- a/lib/ext2fs/ismounted.c
+++ b/lib/ext2fs/ismounted.c
@@ -98,6 +98,7 @@ static errcode_t check_mntent_file(const char 
*mtab_file, const char *file,
  {
  	struct mntent 	*mnt;
  	struct stat	st_buf;
+	struct stat	dir_st_buf;
  	errcode_t	retval = 0;
  	dev_t		file_dev=0, file_rdev=0;
  	ino_t		file_ino=0;
@@ -144,8 +145,12 @@ static errcode_t check_mntent_file(const char 
*mtab_file, const char *file,
  		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
  			if (ext2fsP_is_disk_device(st_buf.st_mode)) {
  #ifndef __GNU__
-				if (file_rdev && (file_rdev == st_buf.st_rdev))
-					break;
+				if (file_rdev && (file_rdev == st_buf.st_rdev)) {
+					if (stat(mnt->mnt_dir, &dir_st_buf) != 0)
+						continue;
+					if (file_rdev == dir_st_buf.st_dev)
+						break;
+				}
  				if (check_loop_mounted(mnt->mnt_fsname,
  						st_buf.st_rdev, file_dev,
  						file_ino) == 1)
-- 
2.23.0

在 2021/11/30 12:04, zhanchengbin 写道:
> If there is a tmpfs with the same name as the disk, and mount before the 
> disk,example:
>      /dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
>      /dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0
> 
> Create a hard link /dev/sdd-ln for the disk and resize2fs it.The items in
> /proc/mounts are traversed, When you get to tmpfs,file!=mnt->mnt_fsname,
> Therefore, the stat(mnt->mnt_fsname, &st_buf) branch is used,However, the
> values of file_rdev and st_buf.st_rdev are the same.As a result, the system
> mistakenly considers that disk is mounted to /root/tmp.As a 
> result,resize2fs
> fails.
> 
> mkdir /root/tmp
> mkdir /root/mnt
> mkfs.ext4 -F -b 1024 -E "resize=10000000" /dev/sdd 32768
> mount -t tmpfs /dev/sdd /root/tmp
> mount /dev/sdd /root/mnt
> ln /dev/sdd /dev/sdd-ln
> resize2fs /dev/sdd-ln 6G
> 
> Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
> Signed-off-by: guiyao@huawei.com
> ---
>   lib/ext2fs/ismounted.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/ext2fs/ismounted.c b/lib/ext2fs/ismounted.c
> index aee7d726..463a82a6 100644
> --- a/lib/ext2fs/ismounted.c
> +++ b/lib/ext2fs/ismounted.c
> @@ -98,6 +98,7 @@ static errcode_t check_mntent_file(const char 
> *mtab_file, const char *file,
>   {
>       struct mntent     *mnt;
>       struct stat    st_buf;
> +    struct stat    dir_st_buf;
>       errcode_t    retval = 0;
>       dev_t        file_dev=0, file_rdev=0;
>       ino_t        file_ino=0;
> @@ -144,8 +145,12 @@ static errcode_t check_mntent_file(const char 
> *mtab_file, const char *file,
>           if (stat(mnt->mnt_fsname, &st_buf) == 0) {
>               if (ext2fsP_is_disk_device(st_buf.st_mode)) {
>   #ifndef __GNU__
> -                if (file_rdev && (file_rdev == st_buf.st_rdev))
> -                    break;
> +                if (file_rdev && (file_rdev == st_buf.st_rdev)) {
> +                    if (stat(mnt->mnt_dir, &dir_st_buf) != 0)
> +                        continue;
> +                    if (file_rdev == dir_st_buf.st_dev)
> +                        break;
> +                }
>                   if (check_loop_mounted(mnt->mnt_fsname,
>                           st_buf.st_rdev, file_dev,
>                           file_ino) == 1)

Re: [PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

[Theodore Ts'o]

On Tue, Nov 30, 2021 at 12:04:48PM +0800, zhanchengbin wrote:
> If there is a tmpfs with the same name as the disk, and mount before the
> disk,example:
> 	/dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
> 	/dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0

This should already be fixed e2fsprogs 1.45.5+ via this commit:

commit ea4d53b7b9079fd6e2cc34cf569a993a183bfbd2
Author: Theodore Ts'o <tytso@mit.edu>
Date:   Sun Nov 10 12:11:49 2019 -0500

    libext2fs/ismounted.c: check device id in advance to skip false device names
    
    If there is a trickster which tries to use device names as the mount
    device for pseudo-file systems, the resulting /proc/mounts can confuse
    ext2fs_check_mount_point().  (So far as I can tell, there's no good
    reason to do this, but sysadmins do the darnest things.)
    
    An example of this might be the following /proc/mounts excerpt:
    
    /dev/sdb /mnt2 tmpfs rw,relatime 0 0
    /dev/sdb /mnt ext4 rw,relatime 0 0
    
    This is created via "mount -t tmpfs /dev/sdb /mnt2" followed via
    "mount -t ext4 /dev/sdb /mnt".  (Normally, a sane mount of tmpfs would
    use something like "mount -t tmpfs tmpfs /mnt2".)
    
    Fix this by double checking the st_rdev of the claimed mountpoint and
    match it with the dev_t of the device.  (Note that the GNU HURD
    doesn't support st_rdev, so we can't solve this problem for the HURD.)
    
    Reported-by: GuiYao <guiyao@huawei.com>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>

I've tested via tst_ismounted and I can't replicate the issue you've described.

% cd /build/e2fsprogs-maint/lib/ext2fs
% make tst_ismounted
% sudo ./tst_ismounted /dev/dm-7
Bogus entry in /proc/mounts!  (/dev/dm-7 is not mounted on /root/tmp)
Device /dev/dm-7 reports flags 11
        /dev/dm-7 is apparently in use.
        /dev/dm-7 is mounted.
        /dev/dm-7 is mounted on /root/mnt.

Cheers,

							- Ted

Re: [PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

[zhanchengbin]

To clarify, commit ea4d53b7b9079fd6e2cc34cf569a993a183bfbd2  does
solve the problem for mounting a disk with the same name as file
  system "tmpfs". However, after mounting it, "ln" command (creating
  a hard link) and "resize2fs" command still report an error.

example:
dev_name="/dev/sdc" (ps: a disk in you self)
mkdir /root/tmp
mkdir /root/mnt
mkfs.ext4 -F -b 1024 -E "resize=10000000" "${dev_name}" 32768
mount -t tmpfs "${dev_name}" /root/tmp
mount "${dev_name}" /root/mnt
ln "${dev_name}" "${dev_name}"-ln
resize2fs "${dev_name}"-ln 6G

You can see the disk is mounted on /root/tmp, but it should be
mounted on /root/mnt actually. I will modify the commit message
  and submit the v2 patch to solve this problem.

在 2021/12/22 4:57, Theodore Ts'o 写道:
> On Tue, Nov 30, 2021 at 12:04:48PM +0800, zhanchengbin wrote:
>> If there is a tmpfs with the same name as the disk, and mount before the
>> disk,example:
>> 	/dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
>> 	/dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0
> 
> This should already be fixed e2fsprogs 1.45.5+ via this commit:
> 
> commit ea4d53b7b9079fd6e2cc34cf569a993a183bfbd2
> Author: Theodore Ts'o <tytso@mit.edu>
> Date:   Sun Nov 10 12:11:49 2019 -0500
> 
>      libext2fs/ismounted.c: check device id in advance to skip false device names
>      
>      If there is a trickster which tries to use device names as the mount
>      device for pseudo-file systems, the resulting /proc/mounts can confuse
>      ext2fs_check_mount_point().  (So far as I can tell, there's no good
>      reason to do this, but sysadmins do the darnest things.)
>      
>      An example of this might be the following /proc/mounts excerpt:
>      
>      /dev/sdb /mnt2 tmpfs rw,relatime 0 0
>      /dev/sdb /mnt ext4 rw,relatime 0 0
>      
>      This is created via "mount -t tmpfs /dev/sdb /mnt2" followed via
>      "mount -t ext4 /dev/sdb /mnt".  (Normally, a sane mount of tmpfs would
>      use something like "mount -t tmpfs tmpfs /mnt2".)
>      
>      Fix this by double checking the st_rdev of the claimed mountpoint and
>      match it with the dev_t of the device.  (Note that the GNU HURD
>      doesn't support st_rdev, so we can't solve this problem for the HURD.)
>      
>      Reported-by: GuiYao <guiyao@huawei.com>
>      Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> 
> I've tested via tst_ismounted and I can't replicate the issue you've described.
> 
> % cd /build/e2fsprogs-maint/lib/ext2fs
> % make tst_ismounted
> % sudo ./tst_ismounted /dev/dm-7
> Bogus entry in /proc/mounts!  (/dev/dm-7 is not mounted on /root/tmp)
> Device /dev/dm-7 reports flags 11
>          /dev/dm-7 is apparently in use.
>          /dev/dm-7 is mounted.
>          /dev/dm-7 is mounted on /root/mnt.
> 
> Cheers,
> 
> 							- Ted
> .
>