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Commit 66cfd4cf authored by Baokun Li's avatar Baokun Li Committed by Greg Kroah-Hartman
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ext4: avoid overlapping preallocations due to overflow 



commit bedc5d34632c21b5adb8ca7143d4c1f794507e4c 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: 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>
Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1e0a5dec

fs/ext4/mballoc.c

+5 −8
Original line number Diff line number Diff line
@@ -3094,8 +3094,7 @@ 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);
@@ -3203,7 +3202,7 @@ 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;
@@ -3213,8 +3212,7 @@ 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 ||
@@ -3243,12 +3241,11 @@ 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);