Messages in this thread | | | Date | Fri, 21 Mar 2003 13:58:19 -0800 (PST) | From | Junfeng Yang <> | Subject | Re: [CHECKER] potential dereference of user pointer errors |
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Thanks a lot for your confirmation! So actually the first copy_from_user is meant to copy in what "*data" points to, not "data".
-Junfeng
On Fri, 21 Mar 2003, Chris Wright wrote:
> * Junfeng Yang (yjf@stanford.edu) wrote: > > > > [BUG] not sure. the dereference occurs at a tainted place. call > > copy_from_user (, data, ), then copy_from_user (, *data, ) > > > > /home/junfeng/linux-2.5.63/sound/core/seq/instr/ainstr_iw.c:92:snd_seq_iwffff_copy_env_from_stream: > > ERROR:TAINTED deferencing "data" tainted by [dist=0][copy_from_user:parm1] > > seems like a bug, although i think it's the first copy_from_user that > would be broken. > > Looks like call flow could be something like: > Store user buf ptr in event.data.ext.ptr. > Call snd_seq_iwffff_put with the event.data.ext.ptr (offset by header bits) > Call snd_seq_iwffff_copy_env_from_stream with &event.data.ext.ptr (offset a > little further). > > Finally, call copy_from_user on &event.data.ext.ptr, which is copying > into an stype. This looks like it's the bug. I don't think the 32 bit > addr should be copied into the stype, rather the 1st 32bits of the data > (IOW copy_from_user(stype, *data,...)). The second copy_from_user (with > *data) copies in the whole iwffff_env_record_t struct which begins with > an stype, so it really looks as if the first copy is broken. Patch > below. Jaroslav? > > thanks, > -chris > -- > Linux Security Modules http://lsm.immunix.org http://lsm.bkbits.net > > ===== instr/ainstr_iw.c 1.3 vs edited ===== > --- 1.3/sound/core/seq/instr/ainstr_iw.c Mon Feb 10 02:39:27 2003 > +++ edited/instr/ainstr_iw.c Fri Mar 21 13:01:32 2003 > @@ -78,7 +78,7 @@ > while (1) { > if (*len < (long)sizeof(__u32)) > return -EINVAL; > - if (copy_from_user(&stype, data, sizeof(stype))) > + if (copy_from_user(&stype, *data, sizeof(stype))) > return -EFAULT; > if (stype == IWFFFF_STRU_WAVE) > return 0; >
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