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ext4: avoid overlapping preallocations due to overflow 

commit bedc5d3463 upstream.

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>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Baokun Li 2023-10-28 14:47:49 +08:00 committed by Greg Kroah-Hartman
parent f2c3a3aa6f
commit f031e15d0b
1 changed files with 5 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
fs/ext4/mballoc.c
View File

@ -4049,8 +4049,7 @@ 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;
struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
@ -4158,7 +4157,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
/* check we don't cross already preallocated blocks */
rcu_read_lock();
list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
ext4_lblk_t pa_end;
loff_t pa_end;
if (pa->pa_deleted)
continue;
@ -4168,8 +4167,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
continue;
}
pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
pa->pa_len);
pa_end = pa_logical_end(EXT4_SB(ac->ac_sb), pa);
/* PA must not overlap original request */
BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
@ -4198,12 +4196,11 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
/* XXX: extra loop to check we really don't overlap preallocations */
rcu_read_lock();
list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
ext4_lblk_t pa_end;
loff_t pa_end;
spin_lock(&pa->pa_lock);
if (pa->pa_deleted == 0) {
pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
pa->pa_len);
pa_end = pa_logical_end(EXT4_SB(ac->ac_sb), pa);
BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
}
spin_unlock(&pa->pa_lock);