ext4: add two helper functions extent_logical_end() and pa_logical_end()

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.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230724121059.11834-2-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 21b903f..4cb13b3 100644 (file)
--- 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 df6b5e7..d7aeb5d 100644 (file)
--- 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,