'Re: R: [uClinux-dev] Problems with 2GB FAT16 SD/CF cards - resolved'

[prev in list] [next in list] [prev in thread] [next in thread] 

List:       uclinux-dev
Subject:    Re: R: [uClinux-dev] Problems with 2GB FAT16 SD/CF cards - resolved
From:       Greg Ungerer <gerg () snapgear ! com>
Date:       2008-06-26 14:35:12
Message-ID: 4863A920.5040508 () snapgear ! com
[Download RAW message or body]

Hi Andrea,

Tarani, Andrea wrote:
> Warning!!
> The problem is not in busybox but in the uClibc.
> When you call the readdir routine the routine alloc a buffer up to the size of file \
> system block (up 64kb for nfs mounted directory). In the __getdents (int fd, char \
> *buf, size_t nbytes) routine, a temporary buffer of that size is allocated on stack \
> and get a stack overflow

Indeed it does. Use of alloca() in uClinux dangerous!

Did you fix this code?

Is there any reason we can't just change that alloca region to
be a local static array?  Or perhaps a one time malloc of that
size (maintained and used for all subsequent calls)?

Regards
Greg

> -----Messaggio originale-----
> Da: uclinux-dev-bounces@uclinux.org [mailto:uclinux-dev-bounces@uclinux.org] Per \
>                 conto di Greg Ungerer
> Inviato: giovedė 26 giugno 2008 8.54
> A: uClinux development list
> Oggetto: Re: [uClinux-dev] Problems with 2GB FAT16 SD/CF cards - resolved
> 
> Hi Wolfgang,
> 
> Wolfgang Mües wrote:
> > DSLINUX (www.dslinux.org) is using mostly SD cards for file system 
> > storage. With the advent of 2 GByte SD cards with FAT16 and 32KByte 
> > clustersize, many user have reported problems (data aborts while 
> > traversing directories).
> > 
> > I have found that busybox needs more stack space to fix this problem.
> > This was a hard-to-nail-down error, because with directory traversal 
> > problems, network scripts fail, gdbserver fails, etc.
> 
> Any chance you can try the newest busybox version in the latest \
> uClinux-dist-test-20080620? 
> According to the comments in its Makefile.flags:
> 
> # Busybox is a stack-fatty so make sure we increase default size # TODO: use "make \
> stksizes" to find & fix big stack users # (we stole scripts/checkstack.pl from the \
> kernel... thanks guys!) # Reduced from 20k to 16k in 1.9.0. FLTFLAGS += -s 16000
> 
> 
> So they have reduced its stack size even further. If this proves to be too small \
> I'll increase before releasing... 
> Regards
> Greg
> 
> 
> 
> > --- trunk/user/busybox/Rules.mak        2007-10-25 18:45:33 UTC (rev 
> > 2027)
> > +++ trunk/user/busybox/Rules.mak        2007-10-26 17:19:23 UTC (rev 
> > 2028)
> > @@ -47,7 +47,8 @@
> > # MAKEFILES      = $(TOPDIR).config
> > endif
> > 
> > -FLTFLAGS       += -s 20000
> > +# Note that 20K stack space is too low if we use 2GB SD cards
> > +FLTFLAGS       += -s 30000
> > 
> > # What OS are you compiling busybox for?  This allows you to include  
> > # OS specific things, syscall overrides, etc.
> > 
> > 
> > 
> 
> --
> ------------------------------------------------------------------------
> Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@snapgear.com
> Secure Computing Corporation                PHONE:       +61 7 3435 2888
> 825 Stanley St,                             FAX:         +61 7 3891 3630
> Woolloongabba, QLD, 4102, Australia         WEB: http://www.SnapGear.com
> _______________________________________________
> uClinux-dev mailing list
> uClinux-dev@uclinux.org
> http://mailman.uclinux.org/mailman/listinfo/uclinux-dev
> This message was resent by uclinux-dev@uclinux.org To unsubscribe see:
> http://mailman.uclinux.org/mailman/options/uclinux-dev
> 
> 
> This message (including any attachments) contains confidential 
> and/or proprietary information intended only for the addressee.  
> Any unauthorized disclosure, copying, distribution or reliance on 
> the contents of this information is strictly prohibited and may 
> constitute a violation of law.  If you are not the intended 
> recipient, please notify the sender immediately by responding to 
> this e-mail, and delete the message from your system.  If you 
> have any questions about this e-mail please notify the sender 
> immediately.
> _______________________________________________
> uClinux-dev mailing list
> uClinux-dev@uclinux.org
> http://mailman.uclinux.org/mailman/listinfo/uclinux-dev
> This message was resent by uclinux-dev@uclinux.org
> To unsubscribe see:
> http://mailman.uclinux.org/mailman/options/uclinux-dev
> 

-- 
------------------------------------------------------------------------
Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@snapgear.com
SnapGear -- a Secure Computing Company      PHONE:       +61 7 3435 2888
825 Stanley St,                             FAX:         +61 7 3891 3630
Woolloongabba, QLD, 4102, Australia         WEB: http://www.SnapGear.com
_______________________________________________
uClinux-dev mailing list
uClinux-dev@uclinux.org
http://mailman.uclinux.org/mailman/listinfo/uclinux-dev
This message was resent by uclinux-dev@uclinux.org
To unsubscribe see:
http://mailman.uclinux.org/mailman/options/uclinux-dev

[prev in list] [next in list] [prev in thread] [next in thread] 