Messages in this thread | | | Date | Thu, 3 Dec 2020 13:37:57 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 1/3] x86/uprobes: Fix not using prefixes.nbytes for loop over prefixes.bytes |
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On Thu, Dec 03, 2020 at 01:50:37PM +0900, Masami Hiramatsu wrote: > Since the insn.prefixes.nbytes can be bigger than the size of > insn.prefixes.bytes[] when a same prefix is repeated, we have to > check whether the insn.prefixes.bytes[i] != 0 and i < 4 instead > of insn.prefixes.nbytes. > This introduces for_each_insn_prefix() macro for this purpose. > > Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints") > Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com > Debugged-by: Kees Cook <keescook@chromium.org> > Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > Cc: stable@vger.kernel.org > --- > Changes in v2: > - Add for_each_insn_prefix() macro and fix to check index first. > --- > arch/x86/include/asm/insn.h | 15 +++++++++++++++ > arch/x86/kernel/uprobes.c | 10 ++++++---- > 2 files changed, 21 insertions(+), 4 deletions(-)
Warning: Kernel ABI header at 'tools/arch/x86/include/asm/insn.h' differs from latest version at 'arch/x86/include/asm/insn.h'
> diff --git a/arch/x86/include/asm/insn.h b/arch/x86/include/asm/insn.h > index 5c1ae3eff9d4..e6b38ebd3a1c 100644 > --- a/arch/x86/include/asm/insn.h > +++ b/arch/x86/include/asm/insn.h > @@ -201,6 +201,21 @@ static inline int insn_offset_immediate(struct insn *insn) > return insn_offset_displacement(insn) + insn->displacement.nbytes; > } > > +/** > + * for_each_insn_prefix() -- Iterate prefixes in the instruction > + * @insn: Pointer to struct insn. > + * @idx: Index storage. > + * @prefix: Prefix byte. > + * > + * Iterate prefix bytes of given @insn. Each prefix byte is stored in @prefix > + * and the index is stored in @idx (note that this @idx is just for a cursor, > + * do not change it.) > + * Since prefixes.nbytes can be bigger than 4 if some prefixes are repeated, > + * we can not use it for looping over the prefixes.
Please use passive voice: no "we" or "I", etc,
> + */ > +#define for_each_insn_prefix(insn, idx, prefix) \ > + for (idx = 0; idx < 4 && (prefix = insn->prefixes.bytes[idx]) != 0; idx++)
Btw, looking at the struct insn definition, that prefixes member should have a comment above it that those are the legacy prefixes which can be <= 4. But that's minor.
In any case, I'll fix up the minor issues now but pls remember to do them in the future.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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