Baokun Li <libaokun1@xxxxxxxxxx> writes:
> When we use lstart + len to calculate the end of free extent or prealloc
> space, it may exceed the maximum value of 4294967295(0xffffffff) supported
> by ext4_lblk_t and cause overflow, which may lead to various problems.
>
> Therefore, we add two helper functions, extent_logical_end() and
> pa_logical_end(), to limit the type of end to loff_t, and also convert
> lstart to loff_t for calculation to avoid overflow.
Sure. extent_logical_end() is not as bad after dropping the third param.
Thanks for addressing review comments and identifying overflow issues :)
Looks good to me. Feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
>
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 9 +++------
> fs/ext4/mballoc.h | 14 ++++++++++++++
> 2 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 21b903fe546e..4cb13b3e41b3 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4432,7 +4432,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
>
> /* first, let's learn actual file size
> * given current request is allocated */
> - size = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
> + size = extent_logical_end(sbi, &ac->ac_o_ex);
> size = size << bsbits;
> if (size < i_size_read(ac->ac_inode))
> size = i_size_read(ac->ac_inode);
> @@ -4766,7 +4766,6 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
> struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
> struct ext4_locality_group *lg;
> struct ext4_prealloc_space *tmp_pa = NULL, *cpa = NULL;
> - loff_t tmp_pa_end;
> struct rb_node *iter;
> ext4_fsblk_t goal_block;
>
> @@ -4862,9 +4861,7 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
> * pa can possibly satisfy the request hence check if it overlaps
> * original logical start and stop searching if it doesn't.
> */
> - tmp_pa_end = (loff_t)tmp_pa->pa_lstart + EXT4_C2B(sbi, tmp_pa->pa_len);
> -
> - if (ac->ac_o_ex.fe_logical >= tmp_pa_end) {
> + if (ac->ac_o_ex.fe_logical >= pa_logical_end(sbi, tmp_pa)) {
> spin_unlock(&tmp_pa->pa_lock);
> goto try_group_pa;
> }
> @@ -5769,7 +5766,7 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
>
> group_pa_eligible = sbi->s_mb_group_prealloc > 0;
> inode_pa_eligible = true;
> - size = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
> + size = extent_logical_end(sbi, &ac->ac_o_ex);
> isize = (i_size_read(ac->ac_inode) + ac->ac_sb->s_blocksize - 1)
> >> bsbits;
>
> diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
> index df6b5e7c2274..d7aeb5da7d86 100644
> --- a/fs/ext4/mballoc.h
> +++ b/fs/ext4/mballoc.h
> @@ -233,6 +233,20 @@ static inline ext4_fsblk_t ext4_grp_offs_to_block(struct super_block *sb,
> (fex->fe_start << EXT4_SB(sb)->s_cluster_bits);
> }
>
> +static inline loff_t extent_logical_end(struct ext4_sb_info *sbi,
> + struct ext4_free_extent *fex)
> +{
> + /* Use loff_t to avoid end exceeding ext4_lblk_t max. */
> + return (loff_t)fex->fe_logical + EXT4_C2B(sbi, fex->fe_len);
> +}
> +
> +static inline loff_t pa_logical_end(struct ext4_sb_info *sbi,
> + struct ext4_prealloc_space *pa)
> +{
> + /* Use loff_t to avoid end exceeding ext4_lblk_t max. */
> + return (loff_t)pa->pa_lstart + EXT4_C2B(sbi, pa->pa_len);
> +}
> +
> typedef int (*ext4_mballoc_query_range_fn)(
> struct super_block *sb,
> ext4_group_t agno,
> --
> 2.31.1
