F_OFD_GETLK implemented wrong with CIFS protocol version 2.0+

F_OFD_GETLK implemented wrong with CIFS protocol version 2.0+

[Laura Abbott]

Hi,

A while back, someone reported a failure on Fedora when trying to boot
a QEMU image off of a CIFS share. The issue was reduced down to a
test case (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c8)

# cat test-ofd-lock.c
#define _GNU_SOURCE
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

int main(int argc, char **argv)
{
     int ret;
     int fd;
     struct flock fl = {
         .l_whence = SEEK_SET,
         .l_start  = 0,
         .l_len    = 0,
         .l_type   = F_RDLCK,
     };
     if (argc < 2) {
             fprintf(stderr, "Usage: %s <file>\n", argv[0]);
             return 1;
     }
     fd = open(argv[1], O_RDWR);
     if (fd < 0) {
             perror("open");
             return errno;
     }
     ret = fcntl(fd, F_OFD_SETLK, &fl);
     if (ret) {
             perror("setlk");
             return errno;
     }
     fl.l_type = F_WRLCK;
     ret = fcntl(fd, F_OFD_GETLK, &fl);
     if (ret) {
             perror("getlk");
             return errno;
     }
     if (fl.l_type != F_UNLCK) {
             fprintf(stderr, "get lock test failed\n");
             return 1;
     }
     return 0;
}
[root@localhost ~]# make test-ofd-lock
cc     test-ofd-lock.c   -o test-ofd-lock
[root@localhost ~]# touch /tmp/test && ./test-ofd-lock /tmp/test
[root@localhost ~]# echo $?
0
[root@localhost ~]# touch /mnt/test && ./test-ofd-lock /mnt/test
get lock test failed
[root@localhost ~]# mount | grep /mnt
//192.168.31.1/tddownload on /mnt type cifs (rw,relatime,vers=3.0,
cache=strict,username=admin,domain=,uid=0,
noforceuid,gid=0,noforcegid,addr=192.168.31.1,file_mode=0755,
dir_mode=0755,nounix,serverino,mapposix,rsize=1048576,
wsize=1048576,echo_interval=60,actimeo=1,user=admin)


As explained by one of the QEMU developers
(https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c37)

'''
It is a kernel bug. The code snippet in comment 8 shows clearly that the kernel
is doing the wrong thing, which cannot be fixed/worked around by QEMU.

In man 2 fcntl:

        F_OFD_GETLK (struct flock *)
               On input to this call, lock describes an open file description lock
we would like to place on the file.  If the lock could  be  placed,  fcntl()  does  not
               actually  place  it,  but  returns F_UNLCK in the l_type field of lock
and leaves the other fields of the structure unchanged.  If one or more incompatible
               locks would prevent this lock being placed, then details about one of
these locks are returned via lock, as described above for F_GETLK.

which is not the case with the new CIFS behaviour.
''

You can read the full context at https://bugzilla.redhat.com/show_bug.cgi?id=1484130

Any suggestions?

Thanks,
Laura

Re: F_OFD_GETLK implemented wrong with CIFS protocol version 2.0+

[Steve French]

We are taking a look at this - Ronnie had some ideas.  Probably simply
not implemented - hopefully not too hard to fix.
On Mon, Jun 25, 2018 at 6:58 PM Laura Abbott <labbott@redhat.com> wrote:
>
> Hi,
>
> A while back, someone reported a failure on Fedora when trying to boot
> a QEMU image off of a CIFS share. The issue was reduced down to a
> test case (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c8)
>
> # cat test-ofd-lock.c
> #define _GNU_SOURCE
> #include <errno.h>
> #include <stdio.h>
> #include <unistd.h>
> #include <fcntl.h>
>
> int main(int argc, char **argv)
> {
>      int ret;
>      int fd;
>      struct flock fl = {
>          .l_whence = SEEK_SET,
>          .l_start  = 0,
>          .l_len    = 0,
>          .l_type   = F_RDLCK,
>      };
>      if (argc < 2) {
>              fprintf(stderr, "Usage: %s <file>\n", argv[0]);
>              return 1;
>      }
>      fd = open(argv[1], O_RDWR);
>      if (fd < 0) {
>              perror("open");
>              return errno;
>      }
>      ret = fcntl(fd, F_OFD_SETLK, &fl);
>      if (ret) {
>              perror("setlk");
>              return errno;
>      }
>      fl.l_type = F_WRLCK;
>      ret = fcntl(fd, F_OFD_GETLK, &fl);
>      if (ret) {
>              perror("getlk");
>              return errno;
>      }
>      if (fl.l_type != F_UNLCK) {
>              fprintf(stderr, "get lock test failed\n");
>              return 1;
>      }
>      return 0;
> }
> [root@localhost ~]# make test-ofd-lock
> cc     test-ofd-lock.c   -o test-ofd-lock
> [root@localhost ~]# touch /tmp/test && ./test-ofd-lock /tmp/test
> [root@localhost ~]# echo $?
> 0
> [root@localhost ~]# touch /mnt/test && ./test-ofd-lock /mnt/test
> get lock test failed
> [root@localhost ~]# mount | grep /mnt
> //192.168.31.1/tddownload on /mnt type cifs (rw,relatime,vers=3.0,
> cache=strict,username=admin,domain=,uid=0,
> noforceuid,gid=0,noforcegid,addr=192.168.31.1,file_mode=0755,
> dir_mode=0755,nounix,serverino,mapposix,rsize=1048576,
> wsize=1048576,echo_interval=60,actimeo=1,user=admin)
>
>
> As explained by one of the QEMU developers
> (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c37)
>
> '''
> It is a kernel bug. The code snippet in comment 8 shows clearly that the kernel
> is doing the wrong thing, which cannot be fixed/worked around by QEMU.
>
> In man 2 fcntl:
>
>         F_OFD_GETLK (struct flock *)
>                On input to this call, lock describes an open file description lock
> we would like to place on the file.  If the lock could  be  placed,  fcntl()  does  not
>                actually  place  it,  but  returns F_UNLCK in the l_type field of lock
> and leaves the other fields of the structure unchanged.  If one or more incompatible
>                locks would prevent this lock being placed, then details about one of
> these locks are returned via lock, as described above for F_GETLK.
>
> which is not the case with the new CIFS behaviour.
> ''
>
> You can read the full context at https://bugzilla.redhat.com/show_bug.cgi?id=1484130
>
> Any suggestions?
>
> Thanks,
> Laura
> --
> To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Thanks,

Steve

Re: F_OFD_GETLK implemented wrong with CIFS protocol version 2.0+

[Ronnie Sahlberg]

The problem is in fs/cifs/file.c:cifs_find_fid_lock_conflict since it is not aware of OFD locks
and thus think there is a conflict.

I have an initial patch that fixes the problem for the reproducer but need more time to understand if/what
else might need fixin.





----- Original Message -----
> From: "Steve French" <smfrench@gmail.com>
> To: labbott@redhat.com
> Cc: "CIFS" <linux-cifs@vger.kernel.org>, "samba-technical" <samba-technical@lists.samba.org>, "LKML"
> <linux-kernel@vger.kernel.org>, "Adam Williamson" <awilliam@redhat.com>
> Sent: Tuesday, 26 June, 2018 1:54:40 PM
> Subject: Re: F_OFD_GETLK implemented wrong with CIFS protocol version 2.0+
> 
> We are taking a look at this - Ronnie had some ideas.  Probably simply
> not implemented - hopefully not too hard to fix.
> On Mon, Jun 25, 2018 at 6:58 PM Laura Abbott <labbott@redhat.com> wrote:
> >
> > Hi,
> >
> > A while back, someone reported a failure on Fedora when trying to boot
> > a QEMU image off of a CIFS share. The issue was reduced down to a
> > test case (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c8)
> >
> > # cat test-ofd-lock.c
> > #define _GNU_SOURCE
> > #include <errno.h>
> > #include <stdio.h>
> > #include <unistd.h>
> > #include <fcntl.h>
> >
> > int main(int argc, char **argv)
> > {
> >      int ret;
> >      int fd;
> >      struct flock fl = {
> >          .l_whence = SEEK_SET,
> >          .l_start  = 0,
> >          .l_len    = 0,
> >          .l_type   = F_RDLCK,
> >      };
> >      if (argc < 2) {
> >              fprintf(stderr, "Usage: %s <file>\n", argv[0]);
> >              return 1;
> >      }
> >      fd = open(argv[1], O_RDWR);
> >      if (fd < 0) {
> >              perror("open");
> >              return errno;
> >      }
> >      ret = fcntl(fd, F_OFD_SETLK, &fl);
> >      if (ret) {
> >              perror("setlk");
> >              return errno;
> >      }
> >      fl.l_type = F_WRLCK;
> >      ret = fcntl(fd, F_OFD_GETLK, &fl);
> >      if (ret) {
> >              perror("getlk");
> >              return errno;
> >      }
> >      if (fl.l_type != F_UNLCK) {
> >              fprintf(stderr, "get lock test failed\n");
> >              return 1;
> >      }
> >      return 0;
> > }
> > [root@localhost ~]# make test-ofd-lock
> > cc     test-ofd-lock.c   -o test-ofd-lock
> > [root@localhost ~]# touch /tmp/test && ./test-ofd-lock /tmp/test
> > [root@localhost ~]# echo $?
> > 0
> > [root@localhost ~]# touch /mnt/test && ./test-ofd-lock /mnt/test
> > get lock test failed
> > [root@localhost ~]# mount | grep /mnt
> > //192.168.31.1/tddownload on /mnt type cifs (rw,relatime,vers=3.0,
> > cache=strict,username=admin,domain=,uid=0,
> > noforceuid,gid=0,noforcegid,addr=192.168.31.1,file_mode=0755,
> > dir_mode=0755,nounix,serverino,mapposix,rsize=1048576,
> > wsize=1048576,echo_interval=60,actimeo=1,user=admin)
> >
> >
> > As explained by one of the QEMU developers
> > (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c37)
> >
> > '''
> > It is a kernel bug. The code snippet in comment 8 shows clearly that the
> > kernel
> > is doing the wrong thing, which cannot be fixed/worked around by QEMU.
> >
> > In man 2 fcntl:
> >
> >         F_OFD_GETLK (struct flock *)
> >                On input to this call, lock describes an open file
> >                description lock
> > we would like to place on the file.  If the lock could  be  placed,
> > fcntl()  does  not
> >                actually  place  it,  but  returns F_UNLCK in the l_type
> >                field of lock
> > and leaves the other fields of the structure unchanged.  If one or more
> > incompatible
> >                locks would prevent this lock being placed, then details
> >                about one of
> > these locks are returned via lock, as described above for F_GETLK.
> >
> > which is not the case with the new CIFS behaviour.
> > ''
> >
> > You can read the full context at
> > https://bugzilla.redhat.com/show_bug.cgi?id=1484130
> >
> > Any suggestions?
> >
> > Thanks,
> > Laura
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
> 
> --
> Thanks,
> 
> Steve
> --
> To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: F_OFD_GETLK implemented wrong with CIFS protocol version 2.0+

[Steve French]

I am glad that there is a fairly simple reproducer, but wondering if
any of the standard Linux file system functional tests (xfstests) use
these - if not would be good to add your test case to xfstests so
these missing features don't slip through.
On Mon, Jun 25, 2018 at 6:58 PM Laura Abbott <labbott@redhat.com> wrote:
>
> Hi,
>
> A while back, someone reported a failure on Fedora when trying to boot
> a QEMU image off of a CIFS share. The issue was reduced down to a
> test case (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c8)
>
> # cat test-ofd-lock.c
> #define _GNU_SOURCE
> #include <errno.h>
> #include <stdio.h>
> #include <unistd.h>
> #include <fcntl.h>
>
> int main(int argc, char **argv)
> {
>      int ret;
>      int fd;
>      struct flock fl = {
>          .l_whence = SEEK_SET,
>          .l_start  = 0,
>          .l_len    = 0,
>          .l_type   = F_RDLCK,
>      };
>      if (argc < 2) {
>              fprintf(stderr, "Usage: %s <file>\n", argv[0]);
>              return 1;
>      }
>      fd = open(argv[1], O_RDWR);
>      if (fd < 0) {
>              perror("open");
>              return errno;
>      }
>      ret = fcntl(fd, F_OFD_SETLK, &fl);
>      if (ret) {
>              perror("setlk");
>              return errno;
>      }
>      fl.l_type = F_WRLCK;
>      ret = fcntl(fd, F_OFD_GETLK, &fl);
>      if (ret) {
>              perror("getlk");
>              return errno;
>      }
>      if (fl.l_type != F_UNLCK) {
>              fprintf(stderr, "get lock test failed\n");
>              return 1;
>      }
>      return 0;
> }
> [root@localhost ~]# make test-ofd-lock
> cc     test-ofd-lock.c   -o test-ofd-lock
> [root@localhost ~]# touch /tmp/test && ./test-ofd-lock /tmp/test
> [root@localhost ~]# echo $?
> 0
> [root@localhost ~]# touch /mnt/test && ./test-ofd-lock /mnt/test
> get lock test failed
> [root@localhost ~]# mount | grep /mnt
> //192.168.31.1/tddownload on /mnt type cifs (rw,relatime,vers=3.0,
> cache=strict,username=admin,domain=,uid=0,
> noforceuid,gid=0,noforcegid,addr=192.168.31.1,file_mode=0755,
> dir_mode=0755,nounix,serverino,mapposix,rsize=1048576,
> wsize=1048576,echo_interval=60,actimeo=1,user=admin)
>
>
> As explained by one of the QEMU developers
> (https://bugzilla.redhat.com/show_bug.cgi?id=1484130#c37)
>
> '''
> It is a kernel bug. The code snippet in comment 8 shows clearly that the kernel
> is doing the wrong thing, which cannot be fixed/worked around by QEMU.
>
> In man 2 fcntl:
>
>         F_OFD_GETLK (struct flock *)
>                On input to this call, lock describes an open file description lock
> we would like to place on the file.  If the lock could  be  placed,  fcntl()  does  not
>                actually  place  it,  but  returns F_UNLCK in the l_type field of lock
> and leaves the other fields of the structure unchanged.  If one or more incompatible
>                locks would prevent this lock being placed, then details about one of
> these locks are returned via lock, as described above for F_GETLK.
>
> which is not the case with the new CIFS behaviour.
> ''
>
> You can read the full context at https://bugzilla.redhat.com/show_bug.cgi?id=1484130
>
> Any suggestions?
>
> Thanks,
> Laura
> --
> To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Thanks,

Steve