Commit bedc5d34 authored by Baokun Li's avatar Baokun Li Committed by Theodore Ts'o
Browse files

ext4: avoid overlapping preallocations due to overflow 



Let's say we want to allocate 2 blocks starting from 4294966386, after
predicting the file size, start is aligned to 4294965248, len is changed
to 2048, then end = start + size = 0x100000000. Since end is of
type ext4_lblk_t, i.e. uint, end is truncated to 0.

This causes (pa->pa_lstart >= end) to always hold when checking if the
current extent to be allocated crosses already preallocated blocks, so the
resulting ac_g_ex may cross already preallocated blocks. Hence we convert
the end type to loff_t and use pa_logical_end() to avoid overflow.

Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230724121059.11834-4-libaokun1@huawei.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent bc056e71

fs/ext4/mballoc.c

+10 −11
Original line number Diff line number Diff line
@@ -4222,12 +4222,13 @@ ext4_mb_pa_rb_next_iter(ext4_lblk_t new_start, ext4_lblk_t cur_start, struct rb_ 


static inline void

ext4_mb_pa_assert_overlap(struct ext4_allocation_context *ac,

			  ext4_lblk_t start, ext4_lblk_t end)

			  ext4_lblk_t start, loff_t end)

{

	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);

	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);

	struct ext4_prealloc_space *tmp_pa;

	ext4_lblk_t tmp_pa_start, tmp_pa_end;

	ext4_lblk_t tmp_pa_start;

	loff_t tmp_pa_end;

	struct rb_node *iter;



	read_lock(&ei->i_prealloc_lock);
@@ -4236,7 +4237,7 @@ ext4_mb_pa_assert_overlap(struct ext4_allocation_context *ac, 
		tmp_pa = rb_entry(iter, struct ext4_prealloc_space,

				  pa_node.inode_node);

		tmp_pa_start = tmp_pa->pa_lstart;

		tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);

		tmp_pa_end = pa_logical_end(sbi, tmp_pa);



		spin_lock(&tmp_pa->pa_lock);

		if (tmp_pa->pa_deleted == 0)
@@ -4258,14 +4259,14 @@ ext4_mb_pa_assert_overlap(struct ext4_allocation_context *ac, 
 */

static inline void

ext4_mb_pa_adjust_overlap(struct ext4_allocation_context *ac,

			  ext4_lblk_t *start, ext4_lblk_t *end)

			  ext4_lblk_t *start, loff_t *end)

{

	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);

	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);

	struct ext4_prealloc_space *tmp_pa = NULL, *left_pa = NULL, *right_pa = NULL;

	struct rb_node *iter;

	ext4_lblk_t new_start, new_end;

	ext4_lblk_t tmp_pa_start, tmp_pa_end, left_pa_end = -1, right_pa_start = -1;

	ext4_lblk_t new_start, tmp_pa_start, right_pa_start = -1;

	loff_t new_end, tmp_pa_end, left_pa_end = -1;



	new_start = *start;

	new_end = *end;
@@ -4284,7 +4285,7 @@ ext4_mb_pa_adjust_overlap(struct ext4_allocation_context *ac, 
		tmp_pa = rb_entry(iter, struct ext4_prealloc_space,

				  pa_node.inode_node);

		tmp_pa_start = tmp_pa->pa_lstart;

		tmp_pa_end = tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);

		tmp_pa_end = pa_logical_end(sbi, tmp_pa);



		/* PA must not overlap original request */

		spin_lock(&tmp_pa->pa_lock);
@@ -4364,8 +4365,7 @@ ext4_mb_pa_adjust_overlap(struct ext4_allocation_context *ac, 
	}



	if (left_pa) {

		left_pa_end =

			left_pa->pa_lstart + EXT4_C2B(sbi, left_pa->pa_len);

		left_pa_end = pa_logical_end(sbi, left_pa);

		BUG_ON(left_pa_end > ac->ac_o_ex.fe_logical);

	}
@@ -4404,8 +4404,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, 
	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);

	struct ext4_super_block *es = sbi->s_es;

	int bsbits, max;

	ext4_lblk_t end;

	loff_t size, start_off;

	loff_t size, start_off, end;

	loff_t orig_size __maybe_unused;

	ext4_lblk_t start;