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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Fri, 22 Jan 2021 16:07:29 +1100
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Subject: [PATCH] lib/arg: Block repeated short options that require an
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argument
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Fuzzing found the following crash:
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search -hhhhhhhhhhhhhf
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We didn't allocate enough option space for 13 hints because the
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allocation code counts the number of discrete arguments (i.e. argc).
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However, the shortopt parsing code will happily keep processing
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a combination of short options without checking if those short
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options require an argument. This means you can easily end writing
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past the allocated option space.
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This fixes a OOB write which can cause heap corruption.
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Fixes: CVE-2021-20225
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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---
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grub-core/lib/arg.c | 13 +++++++++++++
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1 file changed, 13 insertions(+)
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diff --git a/grub-core/lib/arg.c b/grub-core/lib/arg.c
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index 3288609a5e1..537c5e94b83 100644
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--- a/grub-core/lib/arg.c
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+++ b/grub-core/lib/arg.c
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@@ -299,6 +299,19 @@ grub_arg_parse (grub_extcmd_t cmd, int argc, char **argv,
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it can have an argument value. */
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if (*curshort)
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{
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+ /*
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+ * Only permit further short opts if this one doesn't
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+ * require a value.
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+ */
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+ if (opt->type != ARG_TYPE_NONE &&
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+ !(opt->flags & GRUB_ARG_OPTION_OPTIONAL))
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+ {
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+ grub_error (GRUB_ERR_BAD_ARGUMENT,
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+ N_("missing mandatory option for `%s'"),
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+ opt->longarg);
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+ goto fail;
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+ }
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+
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if (parse_option (cmd, opt, 0, usr) || grub_errno)
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goto fail;
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}
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