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- From 4e76b08f7171a8603d74fcafb27409a91f578647 Mon Sep 17 00:00:00 2001
- From: Daniel Axtens <dja@axtens.net>
- Date: Thu, 21 Jan 2021 12:20:49 +1100
- Subject: [PATCH] io/gzio: Catch missing values in huft_build() and bail
- In huft_build(), "v" is a table of values in order of bit length.
- The code later (when setting up table entries in "r") assumes that all
- elements of this array corresponding to a code are initialized and less
- than N_MAX. However, it doesn't enforce this.
- With sufficiently manipulated inputs (e.g. from fuzzing), there can be
- elements of "v" that are not filled. Therefore a lookup into "e" or "d"
- will use an uninitialized value. This can lead to an invalid/OOB read on
- those values, often leading to a crash.
- Signed-off-by: Daniel Axtens <dja@axtens.net>
- Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
- Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
- ---
- grub-core/io/gzio.c | 10 +++++++++-
- 1 file changed, 9 insertions(+), 1 deletion(-)
- diff --git a/grub-core/io/gzio.c b/grub-core/io/gzio.c
- index 4236f0f..19adebe 100644
- --- a/grub-core/io/gzio.c
- +++ b/grub-core/io/gzio.c
- @@ -507,6 +507,7 @@ huft_build (unsigned *b, /* code lengths in bits (all assumed <= BMAX) */
- }
-
- /* Make a table of values in order of bit lengths */
- + grub_memset (v, N_MAX, ARRAY_SIZE (v));
- p = b;
- i = 0;
- do
- @@ -588,11 +589,18 @@ huft_build (unsigned *b, /* code lengths in bits (all assumed <= BMAX) */
- r.v.n = (ush) (*p); /* simple code is just the value */
- p++; /* one compiler does not like *p++ */
- }
- - else
- + else if (*p < N_MAX)
- {
- r.e = (uch) e[*p - s]; /* non-simple--look up in lists */
- r.v.n = d[*p++ - s];
- }
- + else
- + {
- + /* Detected an uninitialised value, abort. */
- + if (h)
- + huft_free (u[0]);
- + return 2;
- + }
-
- /* fill code-like entries with r */
- f = 1 << (k - w);
- --
- 2.14.2
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