From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Fri, 22 Jan 2021 16:07:29 +1100 Subject: [PATCH] lib/arg: Block repeated short options that require an argument Fuzzing found the following crash: search -hhhhhhhhhhhhhf We didn't allocate enough option space for 13 hints because the allocation code counts the number of discrete arguments (i.e. argc). However, the shortopt parsing code will happily keep processing a combination of short options without checking if those short options require an argument. This means you can easily end writing past the allocated option space. This fixes a OOB write which can cause heap corruption. Fixes: CVE-2021-20225 Signed-off-by: Daniel Axtens Reviewed-by: Daniel Kiper --- grub-core/lib/arg.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/grub-core/lib/arg.c b/grub-core/lib/arg.c index 3288609a5..537c5e94b 100644 --- a/grub-core/lib/arg.c +++ b/grub-core/lib/arg.c @@ -299,6 +299,19 @@ grub_arg_parse (grub_extcmd_t cmd, int argc, char **argv, it can have an argument value. */ if (*curshort) { + /* + * Only permit further short opts if this one doesn't + * require a value. + */ + if (opt->type != ARG_TYPE_NONE && + !(opt->flags & GRUB_ARG_OPTION_OPTIONAL)) + { + grub_error (GRUB_ERR_BAD_ARGUMENT, + N_("missing mandatory option for `%s'"), + opt->longarg); + goto fail; + } + if (parse_option (cmd, opt, 0, usr) || grub_errno) goto fail; }