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)
