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Date: Thu, 3 Dec 2020 11:00:20 +0900 From: Masami Hiramatsu <mhiramat@...nel.org> To: Kees Cook <keescook@...omium.org> Cc: x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>, Joerg Roedel <jroedel@...e.de>, Tom Lendacky <thomas.lendacky@....com>, "Gustavo A . R . Silva" <gustavoars@...nel.org>, Jann Horn <jannh@...gle.com>, Srikar Dronamraju <srikar@...ux.vnet.ibm.com>, Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/3] x86/uprobes: Fix not using prefixes.nbytes for loop over prefixes.bytes On Wed, 2 Dec 2020 11:04:41 -0800 Kees Cook <keescook@...omium.org> wrote: > On Wed, Dec 02, 2020 at 05:51:16PM +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. > > > > Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints") > > Cc: stable@...r.kernel.org > > Reported-by: Kees Cook <keescook@...omium.org> > > This should probably be: > > Reported-by: syzbot+9b64b619f10f19d19a7c@...kaller.appspotmail.com > Debugged-by: Kees Cook <keescook@...omium.org> OK, let me fix it. Thank you, > > > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org> > > --- > > arch/x86/kernel/uprobes.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c > > index 3fdaa042823d..bb3ea3705b99 100644 > > --- a/arch/x86/kernel/uprobes.c > > +++ b/arch/x86/kernel/uprobes.c > > @@ -257,7 +257,7 @@ static bool is_prefix_bad(struct insn *insn) > > { > > int i; > > > > - for (i = 0; i < insn->prefixes.nbytes; i++) { > > + for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) { > > insn_attr_t attr; > > > > attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]); > > @@ -746,7 +746,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) > > * Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix. > > * No one uses these insns, reject any branch insns with such prefix. > > */ > > - for (i = 0; i < insn->prefixes.nbytes; i++) { > > + for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) { > > if (insn->prefixes.bytes[i] == 0x66) > > return -ENOTSUPP; > > } > > > > > -- > Kees Cook -- Masami Hiramatsu <mhiramat@...nel.org>
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