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io/gzio: Add init_dynamic_block() clean up if unpacking codes fails

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init_dynamic_block() didn't clean up gzio->tl and td in some error
paths. This left td pointing to part of tl. Then in grub_gzio_close(),
when tl was freed the storage for td would also be freed. The code then
attempts to free td explicitly, performing a UAF and then a double free.

Explicitly clean up tl and td in the error paths.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Daniel Axtens 2021-01-21 00:05:58 +11:00 committed by Daniel Kiper
parent 3334a5e6c8
commit 18490336d9
1 changed files with 9 additions and 3 deletions
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12
grub-core/io/gzio.c
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@ -953,7 +953,7 @@ init_dynamic_block (grub_gzio_t gzio)
if ((unsigned) i + j > n)
{
grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
return;
goto fail;
}
while (j--)
ll[i++] = l;
@ -966,7 +966,7 @@ init_dynamic_block (grub_gzio_t gzio)
if ((unsigned) i + j > n)
{
grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
return;
goto fail;
}
while (j--)
ll[i++] = 0;
@ -981,7 +981,7 @@ init_dynamic_block (grub_gzio_t gzio)
if ((unsigned) i + j > n)
{
grub_error (GRUB_ERR_BAD_COMPRESSED_DATA, "too many codes found");
return;
goto fail;
}
while (j--)
ll[i++] = 0;
@ -1019,6 +1019,12 @@ init_dynamic_block (grub_gzio_t gzio)
/* indicate we're now working on a block */
gzio->code_state = 0;
gzio->block_len++;
return;
fail:
huft_free (gzio->tl);
gzio->td = NULL;
gzio->tl = NULL;
}