libsmbclient - Thread Saftey

[David Collier-Brown]

   I did a scan from a copy of v4-0-test after a git-fetch.  I'll 
clean my directory and refetch it and 3.2-test, unless there is
a specific tree I should use...

--dave

Derrell Lipman wrote:
> On Fri, Oct 3, 2008 at 5:40 PM, David Collier-Brown <davec-b at rogers.com 
> <mailto:davec-b at rogers.com>> wrote:
> 
>      I did a check for MT-safe versus merely async-signal-safe functions in
>     the samba4 libsmbclient, and found a number that need attention:
> 
> 
> Hi David, thanks for reporting these!
> 
> I'm not sure which libsmbclient you're basing this on.  There is no 
> libsmbclient in samba4 unless it's something ancient from the early days 
> of samba4, and I can't find any calls to getpass -- one of the issues 
> you raise -- anyplace in samba3 (master) libsmb_*.c.  I did find one 
> call to it in clidfs.c but I'm not sure if/when that's called by 
> libsmbclient code.
> 
> Please let me know what source tree you were looking at in locating 
> these.  I'm going to create a bug report to keep track of these things 
> so that I can fix them when I have some time.
> 
> Thanks again,
> 
> Derrell
> 
> 
> 
>     1) The MT-safe (or unsafe!) ones were:
> 
>     atof - convert string to double-precision number
>        MT-Level: MT-Safe as  long  as setlocale(3C) is not
>        called to change the locale.
> 
>     Found in:
>     "./libsmbclient.c",
>          4697:          4730:
>     ctime - convert date and time to string
>        MT-Level: MT-Safe , but note that the    return values  for
>      asctime(),  ctime(),  gmtime(),  and
>        localtime()  point  to thread-specific data whose content is
>        overwritten by each call by the same thread.
> 
>     Found in:
>     "./libsmbclient.c",
>          4044:          4050:    
>     getpass - read a string of characters without echo
>        MT-Level: MT-Unsafe
>            This one needs a buffer and a semaphore to protect it,
>            and make it, in effect, a getpass_r
>     Found in:
>     "./clidfs.c",
>          203:    
>     inet_ntoa - Internet address manipulation
>        MT-Level: MT-Unsafe, static buffer is overwritten on
>        each call. Linux and Solaris *may* make this per-thread
>        of the compiler is told to generate MT code...
> 
>     Found in:
>     "./namequery.c",
>          716:          723:          1083:     "./nmblib.c",
>          112:          802:          824:          839:    
>     readdir - read directory
>        The  readdir() function is unsafe in
>        multithreaded applications.  The  readdir_r() function is safe, and
>        should be used instead.
>     Found in:
>     "./libsmb_compat.c",
>          256:  
> 
>     2) The merely Async-Signal-Safe ones follow: as the change something
>     external,
>     two competing threads can fight over the results. If you really need
>     to protect these, you need a semaphore that's visible to all callers
>     of the library.  In general, that's too much work for too little
>     value (;-))
> 
>     chmod - change access permission mode of file
>     close - close a file descriptor
>     creat - create a new file or rewrite an existing one
>     fstat - get file status
>     geteuid - get real user, effective user, real group, and effective
>     group IDs
>     getuid - get real user, effective user, real group, and effective
>     group IDs
>     kill - send a signal to a process or a group of processes
>     lseek - move read/write file pointer
>     mkdir - make a directory
>     open - open a file
>     read - read from file
>     rename - change the name of a file
>     rmdir - remove a directory
>     stat - get file status
>     time - get time
>     unlink - remove directory entry
>     write - write on a file
> 
>     --dave
> 
> 
> 
> 
> 
>     Jeremy Allison wrote:
> 
>         On Fri, Oct 03, 2008 at 10:46:14AM -0400, Derrell Lipman wrote:
> 
>             On Fri, Oct 3, 2008 at 10:14 AM, Pane, Chris
>             <cpane at vanteon.com <mailto:cpane at vanteon.com>> wrote:
> 
> 
>                 I have been using libsmbclient to do some smb share
>                 browsing in an
>                 application. I have read that it is currently not thread
>                 safe in samba-3.x.
>                 Anyone know if there are plans for it to be made
>                 thread-safe in samba4?
> 
> 
> 
>             Hi Chris,
> 
>             I believe I've eliminated all non-thread-safe issues from within
>             libsmbclient itself (although that will require a thorough
>             inspection to
>             confirm), but the core functions within samba that
>             libsmbclient calls have
>             not been thread-safe.  Samba4 interfaces are, I think,
>             inherently
>             thread-safe.  Therefore, although no work has begun yet on
>             creating a samba4
>             version of libsmbclient (and it's not yet scheduled), I
>             don't believe
>             there's any reason why a samba4 libsmbclient can't or won't
>             be thread-safe.
> 
> 
> 
>         The easiest thing to do at the moment is wrap the libsmbclient
>         functions in a mutex. I'm looking at making the underlying
>         functions thread safe, but that's a longer term job.
> 
>         Jeremy.
> 
> 
>     -- 
>     David Collier-Brown,         | Always do right. This will gratify
>     System Programmer and Author | some people and astonish the rest
>     davecb at spamcop.net <mailto:davecb at spamcop.net>           |          
>                -- Mark Twain
>     (416) 223-5943
> 
> 

-- 
David Collier-Brown            | Always do right. This will gratify
Sun Microsystems, Toronto      | some people and astonish the rest
davecb at sun.com                 |                      -- Mark Twain
cell: (647) 833-9377, bridge: (877) 385-4099 code: 506 9191#