Messages in this thread | | | Date | Fri, 16 Oct 2020 15:20:44 +0200 | From | Greg KH <> | Subject | Re: [PATCH 3/3] vt: keyboard, extend func_buf_lock to readers |
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On Fri, Oct 16, 2020 at 02:24:12PM +0200, Jiri Slaby wrote: > Both read-side users of func_table/func_buf need locking. Without that, > one can easily confuse the code by repeatedly setting altering strings > like: > while (1) > for (a = 0; a < 2; a++) { > struct kbsentry kbs = {}; > strcpy((char *)kbs.kb_string, a ? ".\n" : "88888\n"); > ioctl(fd, KDSKBSENT, &kbs); > } > > When that program runs, one can get unexpected output by holding F1 > (note the unxpected period on the last line): > . > 88888 > .8888 > > So protect all accesses to 'func_table' (and func_buf) by preexisting > 'func_buf_lock'. > > It is easy in 'k_fn' handler as 'puts_queue' is expected not to sleep. > On the other hand, KDGKBSENT needs a local (atomic) copy of the string > because copy_to_user can sleep. > > Likely fixes CVE-2020-25656. > > Signed-off-by: Jiri Slaby <jslaby@suse.cz> > Reported-by: Minh Yuan <yuanmingbuaa@gmail.com> > --- > drivers/tty/vt/keyboard.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-)
So all 3 of these should go to 5.10-final?
thanks,
greg k-h
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