Messages in this thread | | | From | "Metzger, Markus T" <> | Date | Mon, 22 Dec 2008 15:02:09 +0000 | Subject | RE: [patch] x86, ptrace: require admin privileges for ptrace BTS extension |
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>-----Original Message----- >From: stephane eranian [mailto:eranian@googlemail.com] >Sent: Montag, 22. Dezember 2008 14:24 >To: Metzger, Markus T
>On Mon, Dec 22, 2008 at 1:02 PM, Markus Metzger ><markus.t.metzger@intel.com> wrote: >> Require admin privileges for ptrace BTS extension. >> >Can you explain the motivations for this? > >I thought the BTS extension was a per-process functionality. >So how come I can debug and single step my process without >admin privilege and I cannot capture its own branches. Does this >have to do with user vs. kernel execution of the proces (BTS >captures everything if I recall)?
Ingo requested this as a precaution. We found a bug: the DS context pointer is not cleared on fork. The bug is fixed in tip/master but the fix is considered too intrusive to be promoted that late. The restriction will be removed once the fix is in.
regards, markus.
> >Thanks. > >> >> Reported-by: Ingo Molnar <mingo@elte.hu> >> Signed-off-by: Markus Metzger <markus.t.metzger@intel.com> >> --- >> >> Index: gits/arch/x86/kernel/ptrace.c >> =================================================================== >> --- gits.orig/arch/x86/kernel/ptrace.c 2008-12-22 >09:09:25.000000000 +0100 >> +++ gits/arch/x86/kernel/ptrace.c 2008-12-22 >11:03:01.000000000 +0100 >> @@ -21,6 +21,7 @@ >> #include <linux/audit.h> >> #include <linux/seccomp.h> >> #include <linux/signal.h> >> +#include <linux/capability.h> >> >> #include <asm/uaccess.h> >> #include <asm/pgtable.h> >> @@ -742,6 +743,10 @@ >> struct ptrace_bts_config cfg; >> int error = 0; >> >> + error = -EPERM; >> + if (!capable(CAP_SYS_ADMIN)) >> + goto errout; >> + >> error = -EOPNOTSUPP; >> if (!bts_cfg.sizeof_bts) >> goto errout; >> --------------------------------------------------------------------- >> Intel GmbH >> Dornacher Strasse 1 >> 85622 Feldkirchen/Muenchen Germany >> Sitz der Gesellschaft: Feldkirchen bei Muenchen >> Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer >> Registergericht: Muenchen HRB 47456 Ust.-IdNr. >> VAT Registration No.: DE129385895 >> Citibank Frankfurt (BLZ 502 109 00) 600119052 >> >> This e-mail and any attachments may contain confidential material for >> the sole use of the intended recipient(s). Any review or distribution >> by others is strictly prohibited. If you are not the intended >> recipient, please contact the sender and delete all copies. >> >> > --------------------------------------------------------------------- Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen Germany Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer Registergericht: Muenchen HRB 47456 Ust.-IdNr. VAT Registration No.: DE129385895 Citibank Frankfurt (BLZ 502 109 00) 600119052
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