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: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230724121059.11834-4-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 86bce87..78a4a24 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -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;