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DescriptionRoberto Bergantinos
2020-04-22 12:12:11 UTC
Description of problem:
This is an issue exposed after introducing commit 597807396a00e6f31aa03805ddca27875b81440b.
util-linux-2.23.2-61.el7.x86_64 on RHEL7.
To reproduce :
=====================================================
[root@rhel76-2 ~]# rpm -qa util-linux
util-linux-2.23.2-61.el7.x86_64
[root@rhel76-2 ~]# stap -gve 'probe module("cifs").function("smb2_is_path_accessible").return{if (kernel_string(@entry($full_path)) == "") $return = 1}' &
[1] 17722
[root@rhel76-2 ~]# Pass 1: parsed user script and 473 library scripts using 271748virt/69120res/3484shr/65780data kb, in 780usr/60sys/856real ms.
Pass 2: analyzed script: 2 probes, 4 functions, 3 embeds, 2 globals using 396980virt/195636res/4824shr/191012data kb, in 1010usr/650sys/1659real ms.
Pass 3: translated to C into "/tmp/stapqm3al5/stap_3c10a53c53d36460ed73aac03fc2c4a6_3953_src.c" using 396980virt/195964res/5152shr/191012data kb, in 470usr/130sys/599real ms.
Pass 4: compiled C into "stap_3c10a53c53d36460ed73aac03fc2c4a6_3953.ko" in 1790usr/500sys/2082real ms.
Pass 5: starting run.
[root@rhel76-2 ~]# umount /mnt
[root@rhel76-2 ~]# grep cifs /etc/fstab
//rhel73/myshare/sub/path /mnt cifs vers=3.0,username=roberto,password=Armt002!,uid=1000,gid=1000,dir_mode=0777,file_mode=0666 0 0
[root@rhel76-2 ~]# mount -vvv -a
/ : ignored
/boot : already mounted
swap : ignored
mount.cifs kernel mount options: ip=172.23.1.225,unc=\\rhel73\myshare,vers=3.0,dir_mode=0777,file_mode=0666,uid=1000,gid=1000,user=roberto,prefixpath=sub/path,pass=********
/mnt : successfully mounted
[root@rhel76-2 ~]# grep cifs /proc/self/mountinfo
47 39 0:40 / /mnt rw,relatime shared:60 - cifs //rhel73/myshare/sub/path rw,vers=3.0,cache=strict,username=roberto,domain=RHEL73,uid=1000,forceuid,gid=1000,forcegid,addr=172.23.1.225,file_mode=0666,dir_mode=0777,soft,nounix,serverino,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1
[root@rhel76-2 ~]# mount -vvv -a
/ : ignored
/boot : already mounted
swap : ignored
mount.cifs kernel mount options: ip=172.23.1.225,unc=\\rhel73\myshare,vers=3.0,dir_mode=0777,file_mode=0666,uid=1000,gid=1000,user=roberto,prefixpath=sub/path,pass=********
mount error(16): Device or resource busy
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) <<<==== we still try the mount
[root@rhel76-2 ~]# fg
stap -gve 'probe module("cifs").function("smb2_is_path_accessible").return{if (kernel_string(@entry($full_path)) == "") $return = 1}'
^CPass 5: run completed in 30usr/180sys/45603real ms.
[root@rhel76-2 ~]# dmesg | tail -1
[91858.915331] CIFS VFS: cannot query dirs between root and final path, enabling CIFS_MOUNT_USE_PREFIX_PATH [1]
=====================================================
The underlying problem is that with the new code from 1633657 we introduce this on mnt_table_is_fs_mounted :
+ if (strcmp(mnt_fs_get_fstype(fs), "cifs") == 0) {
+ const char *unc_subdir = get_cifs_unc_subdir_path(src);
+ const char *path_on_fs = mnt_fs_get_root(fs);
+ if (!unc_subdir || !path_on_fs || !streq_paths(unc_subdir, path_on_fs))
+ continue;
But path_on_fs will be set to "/" on mountinfo if we cannot query root dirs [1] :
[root@rhel76-2 /]# grep cifs /proc/self/mountinfo
47 39 0:40 / /mnt rw,relatime shared:60 - cifs //rhel73/myshare/sub/path ...
^
For good case when we can query up until root :
[root@rhel76-2 /]# grep cifs /proc/self/mountinfo
47 39 0:40 /sub/path /mnt rw,relatime shared:60 - cifs //rhel73/myshare/sub/path ...
^^^^^^^^^
That is so since on kernel cifs code, cifs_get_root (which returns the entry associated with mnt_root)
return s_root if CIFS_MOUNT_USE_PREFIX_PATH is set, no questions asked.
This situation can occurr often on CIFS mounts, as CIFS servers limit frequently scope of access to the root path.
As as consequence streq_paths will return 0 and we'll skip this entry on mnt_table_is_fs_mounted
This can be reproduce on RHEL8 and probably on upstream.
I think this commit may help :
From: Roberto Bergantinos Corpas <rbergant>
Date: Wed, 22 Apr 2020 12:27:04 +0200
Subject: [PATCH] fix for EBUSY on cifs mounts
---
libmount/src/tab.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index 3ee9c00..bc11e6a 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -1169,7 +1169,8 @@ int mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_fs)
if (strcmp(mnt_fs_get_fstype(fs), "cifs") == 0) {
const char *unc_subdir = get_cifs_unc_subdir_path(src);
const char *path_on_fs = mnt_fs_get_root(fs);
- if (!unc_subdir || !path_on_fs || !streq_paths(unc_subdir, path_on_fs))
+ if (!unc_subdir || !path_on_fs || (!streq_paths(unc_subdir, path_on_fs) &&
+ !(streq_paths("/", path_on_fs))))
continue;
} else {
const char *r = mnt_fs_get_root(fs);
--
2.21.0
I've tested on RHEL7 for either this issue and 1633657 and neither are reproduced. Not sure if this may trigger
any "false positive" since mount source is already checked here, but im not sure so opening this for review and reporting
Version-Release number of selected component (if applicable):
How reproducible: 100%
Steps to Reproduce: See above
1.
2.
3.
Actual results:
Expected results:
Additional info:
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (util-linux bug fix and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2020:3963
Description of problem: This is an issue exposed after introducing commit 597807396a00e6f31aa03805ddca27875b81440b. util-linux-2.23.2-61.el7.x86_64 on RHEL7. To reproduce : ===================================================== [root@rhel76-2 ~]# rpm -qa util-linux util-linux-2.23.2-61.el7.x86_64 [root@rhel76-2 ~]# stap -gve 'probe module("cifs").function("smb2_is_path_accessible").return{if (kernel_string(@entry($full_path)) == "") $return = 1}' & [1] 17722 [root@rhel76-2 ~]# Pass 1: parsed user script and 473 library scripts using 271748virt/69120res/3484shr/65780data kb, in 780usr/60sys/856real ms. Pass 2: analyzed script: 2 probes, 4 functions, 3 embeds, 2 globals using 396980virt/195636res/4824shr/191012data kb, in 1010usr/650sys/1659real ms. Pass 3: translated to C into "/tmp/stapqm3al5/stap_3c10a53c53d36460ed73aac03fc2c4a6_3953_src.c" using 396980virt/195964res/5152shr/191012data kb, in 470usr/130sys/599real ms. Pass 4: compiled C into "stap_3c10a53c53d36460ed73aac03fc2c4a6_3953.ko" in 1790usr/500sys/2082real ms. Pass 5: starting run. [root@rhel76-2 ~]# umount /mnt [root@rhel76-2 ~]# grep cifs /etc/fstab //rhel73/myshare/sub/path /mnt cifs vers=3.0,username=roberto,password=Armt002!,uid=1000,gid=1000,dir_mode=0777,file_mode=0666 0 0 [root@rhel76-2 ~]# mount -vvv -a / : ignored /boot : already mounted swap : ignored mount.cifs kernel mount options: ip=172.23.1.225,unc=\\rhel73\myshare,vers=3.0,dir_mode=0777,file_mode=0666,uid=1000,gid=1000,user=roberto,prefixpath=sub/path,pass=******** /mnt : successfully mounted [root@rhel76-2 ~]# grep cifs /proc/self/mountinfo 47 39 0:40 / /mnt rw,relatime shared:60 - cifs //rhel73/myshare/sub/path rw,vers=3.0,cache=strict,username=roberto,domain=RHEL73,uid=1000,forceuid,gid=1000,forcegid,addr=172.23.1.225,file_mode=0666,dir_mode=0777,soft,nounix,serverino,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1 [root@rhel76-2 ~]# mount -vvv -a / : ignored /boot : already mounted swap : ignored mount.cifs kernel mount options: ip=172.23.1.225,unc=\\rhel73\myshare,vers=3.0,dir_mode=0777,file_mode=0666,uid=1000,gid=1000,user=roberto,prefixpath=sub/path,pass=******** mount error(16): Device or resource busy Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) <<<==== we still try the mount [root@rhel76-2 ~]# fg stap -gve 'probe module("cifs").function("smb2_is_path_accessible").return{if (kernel_string(@entry($full_path)) == "") $return = 1}' ^CPass 5: run completed in 30usr/180sys/45603real ms. [root@rhel76-2 ~]# dmesg | tail -1 [91858.915331] CIFS VFS: cannot query dirs between root and final path, enabling CIFS_MOUNT_USE_PREFIX_PATH [1] ===================================================== The underlying problem is that with the new code from 1633657 we introduce this on mnt_table_is_fs_mounted : + if (strcmp(mnt_fs_get_fstype(fs), "cifs") == 0) { + const char *unc_subdir = get_cifs_unc_subdir_path(src); + const char *path_on_fs = mnt_fs_get_root(fs); + if (!unc_subdir || !path_on_fs || !streq_paths(unc_subdir, path_on_fs)) + continue; But path_on_fs will be set to "/" on mountinfo if we cannot query root dirs [1] : [root@rhel76-2 /]# grep cifs /proc/self/mountinfo 47 39 0:40 / /mnt rw,relatime shared:60 - cifs //rhel73/myshare/sub/path ... ^ For good case when we can query up until root : [root@rhel76-2 /]# grep cifs /proc/self/mountinfo 47 39 0:40 /sub/path /mnt rw,relatime shared:60 - cifs //rhel73/myshare/sub/path ... ^^^^^^^^^ That is so since on kernel cifs code, cifs_get_root (which returns the entry associated with mnt_root) return s_root if CIFS_MOUNT_USE_PREFIX_PATH is set, no questions asked. This situation can occurr often on CIFS mounts, as CIFS servers limit frequently scope of access to the root path. As as consequence streq_paths will return 0 and we'll skip this entry on mnt_table_is_fs_mounted This can be reproduce on RHEL8 and probably on upstream. I think this commit may help : From: Roberto Bergantinos Corpas <rbergant> Date: Wed, 22 Apr 2020 12:27:04 +0200 Subject: [PATCH] fix for EBUSY on cifs mounts --- libmount/src/tab.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/libmount/src/tab.c b/libmount/src/tab.c index 3ee9c00..bc11e6a 100644 --- a/libmount/src/tab.c +++ b/libmount/src/tab.c @@ -1169,7 +1169,8 @@ int mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_fs) if (strcmp(mnt_fs_get_fstype(fs), "cifs") == 0) { const char *unc_subdir = get_cifs_unc_subdir_path(src); const char *path_on_fs = mnt_fs_get_root(fs); - if (!unc_subdir || !path_on_fs || !streq_paths(unc_subdir, path_on_fs)) + if (!unc_subdir || !path_on_fs || (!streq_paths(unc_subdir, path_on_fs) && + !(streq_paths("/", path_on_fs)))) continue; } else { const char *r = mnt_fs_get_root(fs); -- 2.21.0 I've tested on RHEL7 for either this issue and 1633657 and neither are reproduced. Not sure if this may trigger any "false positive" since mount source is already checked here, but im not sure so opening this for review and reporting Version-Release number of selected component (if applicable): How reproducible: 100% Steps to Reproduce: See above 1. 2. 3. Actual results: Expected results: Additional info: