linux-ext4 - [PATCH AUTOSEL 6.4 04/11] ext4: add two helper functions extent_logical_end() and pa_logical

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Date:   Fri,  8 Sep 2023 20:22:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Baokun Li <libaokun1@...wei.com>,
        Ritesh Harjani <ritesh.list@...il.com>,
        Theodore Ts'o <tytso@....edu>, Sasha Levin <sashal@...nel.org>,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 6.4 04/11] ext4: add two helper functions extent_logical_end() and pa_logical_end()

From: Baokun Li <libaokun1@...wei.com>

[ Upstream commit 43bbddc067883d94de7a43d5756a295439fbe37d ]

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@...wei.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
Link: https://lore.kernel.org/r/20230724121059.11834-2-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 3fa5de892d89d..f17c1573c2a65 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4246,7 +4246,7 @@ 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);
@@ -4570,7 +4570,6 @@ 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;
 
@@ -4666,9 +4665,7 @@ 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;
 	}
@@ -5573,7 +5570,7 @@ 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 6d85ee8674a64..f2b1d4fd98693 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -219,6 +219,20 @@ 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,
-- 
2.40.1