Looks good to me, thanks for refresh the patch!
On Tue, Dec 31, 2019 at 8:57 AM Theodore Y. Ts'o <tytso@xxxxxxx> wrote:
>
> Here is the version which I plan to use in e2fsprogs's maint branch.
>
> - Ted
>
> commit aacc234471a9a0ab6d8d6f610a0e4996e9bfc785
> Author: Wang Shilong <wshilong@xxxxxxx>
> Date: Mon Dec 30 19:52:39 2019 -0500
>
> e2fsck: fix use after free in calculate_tree()
>
> The problem is alloc_blocks() will call get_next_block() which might
> reallocate outdir->buf, and memory address could be changed after
> this. To fix this, pointers that point into outdir->buf, such as
> int_limit and root need to be recaulated based on the new starting
> address of outdir->buf.
>
> [ Changed to correctly recalculate int_limit, and to optimize how we
> reallocate outdir->buf. -TYT ]
>
> Signed-off-by: Wang Shilong <wshilong@xxxxxxx>
> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
>
> diff --git a/e2fsck/rehash.c b/e2fsck/rehash.c
> index 392cfe9f..54bc6803 100644
> --- a/e2fsck/rehash.c
> +++ b/e2fsck/rehash.c
> @@ -301,7 +301,11 @@ static errcode_t get_next_block(ext2_filsys fs, struct out_dir *outdir,
> errcode_t retval;
>
> if (outdir->num >= outdir->max) {
> - retval = alloc_size_dir(fs, outdir, outdir->max + 50);
> + int increment = outdir->max / 10;
> +
> + if (increment < 50)
> + increment = 50;
> + retval = alloc_size_dir(fs, outdir, outdir->max + increment);
> if (retval)
> return retval;
> }
> @@ -645,6 +649,9 @@ static int alloc_blocks(ext2_filsys fs,
> if (retval)
> return retval;
>
> + /* outdir->buf might be reallocated */
> + *prev_ent = (struct ext2_dx_entry *) (outdir->buf + *prev_offset);
> +
> *next_ent = set_int_node(fs, block_start);
> *limit = (struct ext2_dx_countlimit *)(*next_ent);
> if (next_offset)
> @@ -734,6 +741,9 @@ static errcode_t calculate_tree(ext2_filsys fs,
> return retval;
> }
> if (c3 == 0) {
> + int delta1 = (char *)int_limit - outdir->buf;
> + int delta2 = (char *)root - outdir->buf;
> +
> retval = alloc_blocks(fs, &limit, &int_ent,
> &dx_ent, &int_offset,
> NULL, outdir, i, &c2,
> @@ -741,6 +751,11 @@ static errcode_t calculate_tree(ext2_filsys fs,
> if (retval)
> return retval;
>
> + /* outdir->buf might be reallocated */
> + int_limit = (struct ext2_dx_countlimit *)
> + (outdir->buf + delta1);
> + root = (struct ext2_dx_entry *)
> + (outdir->buf + delta2);
> }
> dx_ent->block = ext2fs_cpu_to_le32(i);
> if (c3 != limit->limit)
>
