Description for this pull request:

- Fix a remount failure caused by differing process masks by inheriting
    the original mount options during the remount process.
  - Fix a potential divide-by-zero error and system crash in
    exfat_allocate_bitmap that occurred when the readahead count was zero.
  - Add validation for directory cluster bitmap bits to prevent directory
    and root cluster from being incorrectly zeroed out on corrupted images.
  - Clear the post-EOF page cache when extending a file to prevent stale
    mmap data from becoming visible, addressing an generic/363 failure.
  - Fix a reference count leak in exfat_find by properly releasing
    the dentry set in specific error paths.
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Merge tag 'exfat-for-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat

Pull exfat updates from Namjae Jeon:

 - Fix a remount failure caused by differing process masks by inheriting
   the original mount options during the remount process

 - Fix a potential divide-by-zero error and system crash in
   exfat_allocate_bitmap that occurred when the readahead count was zero

 - Add validation for directory cluster bitmap bits to prevent directory
   and root cluster from being incorrectly zeroed out on corrupted
   images

 - Clear the post-EOF page cache when extending a file to prevent stale
   mmap data from becoming visible, addressing an generic/363 failure

 - Fix a reference count leak in exfat_find by properly releasing the
   dentry set in specific error paths

* tag 'exfat-for-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/exfat:
  exfat: fix remount failure in different process environments
  exfat: fix divide-by-zero in exfat_allocate_bitmap
  exfat: validate the cluster bitmap bits of directory
  exfat: zero out post-EOF page cache on file extension
  exfat: fix refcount leak in exfat_find

fs/exfat/balloc.c

@@ -106,7 +106,7 @@ static int exfat_allocate_bitmap(struct super_block *sb,
 		(PAGE_SHIFT - sb->s_blocksize_bits);
 	for (i = 0; i < sbi->map_sectors; i++) {
 		/* Trigger the next readahead in advance. */
-		if (0 == (i % max_ra_count)) {
+		if (max_ra_count && 0 == (i % max_ra_count)) {
 			blk_start_plug(&plug);
 			for (j = i; j < min(max_ra_count, sbi->map_sectors - i) + i; j++)
 				sb_breadahead(sb, sector + j);
@@ -183,11 +183,10 @@ void exfat_free_bitmap(struct exfat_sb_info *sbi)
 	kvfree(sbi->vol_amap);
 }
 
-int exfat_set_bitmap(struct inode *inode, unsigned int clu, bool sync)
+int exfat_set_bitmap(struct super_block *sb, unsigned int clu, bool sync)
 {
 	int i, b;
 	unsigned int ent_idx;
-	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 
 	if (!is_valid_cluster(sbi, clu))
@@ -202,11 +201,10 @@ int exfat_set_bitmap(struct inode *inode, unsigned int clu, bool sync)
 	return 0;
 }
 
-int exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync)
+int exfat_clear_bitmap(struct super_block *sb, unsigned int clu, bool sync)
 {
 	int i, b;
 	unsigned int ent_idx;
-	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 
 	if (!is_valid_cluster(sbi, clu))
@@ -226,6 +224,28 @@ int exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync)
 	return 0;
 }
 
+bool exfat_test_bitmap(struct super_block *sb, unsigned int clu)
+{
+	int i, b;
+	unsigned int ent_idx;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+
+	if (!sbi->vol_amap)
+		return true;
+
+	if (!is_valid_cluster(sbi, clu))
+		return false;
+
+	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
+	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
+	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);
+
+	if (!test_bit_le(b, sbi->vol_amap[i]->b_data))
+		return false;
+
+	return true;
+}
+
 /*
  * If the value of "clu" is 0, it means cluster 2 which is the first cluster of
  * the cluster heap.

fs/exfat/dir.c

@@ -604,6 +604,11 @@ static int exfat_find_location(struct super_block *sb, struct exfat_chain *p_dir
 	if (ret)
 		return ret;
 
+	if (!exfat_test_bitmap(sb, clu)) {
+		exfat_err(sb, "failed to test cluster bit(%u)", clu);
+		return -EIO;
+	}
+
 	/* byte offset in cluster */
 	off = EXFAT_CLU_OFFSET(off, sbi);
 

fs/exfat/exfat_fs.h

@@ -452,8 +452,9 @@ int exfat_count_num_clusters(struct super_block *sb,
 /* balloc.c */
 int exfat_load_bitmap(struct super_block *sb);
 void exfat_free_bitmap(struct exfat_sb_info *sbi);
-int exfat_set_bitmap(struct inode *inode, unsigned int clu, bool sync);
+int exfat_set_bitmap(struct super_block *sb, unsigned int clu, bool sync);
-int exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync);
+int exfat_clear_bitmap(struct super_block *sb, unsigned int clu, bool sync);
+bool exfat_test_bitmap(struct super_block *sb, unsigned int clu);
 unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu);
 int exfat_count_used_clusters(struct super_block *sb, unsigned int *ret_count);
 int exfat_trim_fs(struct inode *inode, struct fstrim_range *range);

fs/exfat/fatent.c

@@ -205,7 +205,7 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
 				cur_cmap_i = next_cmap_i;
 			}
 
-			err = exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
+			err = exfat_clear_bitmap(sb, clu, (sync && IS_DIRSYNC(inode)));
 			if (err)
 				break;
 			clu++;
@@ -233,7 +233,7 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
 				cur_cmap_i = next_cmap_i;
 			}
 
-			if (exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode))))
+			if (exfat_clear_bitmap(sb, clu, (sync && IS_DIRSYNC(inode))))
 				break;
 
 			if (sbi->options.discard) {
@@ -409,7 +409,7 @@ int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 		}
 
 		/* update allocation bitmap */
-		if (exfat_set_bitmap(inode, new_clu, sync_bmap)) {
+		if (exfat_set_bitmap(sb, new_clu, sync_bmap)) {
 			ret = -EIO;
 			goto free_cluster;
 		}

fs/exfat/file.c

@@ -25,6 +25,8 @@ static int exfat_cont_expand(struct inode *inode, loff_t size)
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct exfat_chain clu;
 
+	truncate_pagecache(inode, i_size_read(inode));
+
 	ret = inode_newsize_ok(inode, size);
 	if (ret)
 		return ret;
@@ -639,6 +641,9 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 
 	inode_lock(inode);
 
+	if (pos > i_size_read(inode))
+		truncate_pagecache(inode, i_size_read(inode));
+
 	valid_size = ei->valid_size;
 
 	ret = generic_write_checks(iocb, iter);

fs/exfat/namei.c

@@ -645,16 +645,6 @@ static int exfat_find(struct inode *dir, const struct qstr *qname,
 	info->valid_size = le64_to_cpu(ep2->dentry.stream.valid_size);
 	info->size = le64_to_cpu(ep2->dentry.stream.size);
 
-	if (info->valid_size < 0) {
-		exfat_fs_error(sb, "data valid size is invalid(%lld)", info->valid_size);
-		return -EIO;
-	}
-
-	if (unlikely(EXFAT_B_TO_CLU_ROUND_UP(info->size, sbi) > sbi->used_clusters)) {
-		exfat_fs_error(sb, "data size is invalid(%lld)", info->size);
-		return -EIO;
-	}
-
 	info->start_clu = le32_to_cpu(ep2->dentry.stream.start_clu);
 	if (!is_valid_cluster(sbi, info->start_clu) && info->size) {
 		exfat_warn(sb, "start_clu is invalid cluster(0x%x)",
@@ -692,6 +682,16 @@ static int exfat_find(struct inode *dir, const struct qstr *qname,
 			     0);
 	exfat_put_dentry_set(&es, false);
 
+	if (info->valid_size < 0) {
+		exfat_fs_error(sb, "data valid size is invalid(%lld)", info->valid_size);
+		return -EIO;
+	}
+
+	if (unlikely(EXFAT_B_TO_CLU_ROUND_UP(info->size, sbi) > sbi->used_clusters)) {
+		exfat_fs_error(sb, "data size is invalid(%lld)", info->size);
+		return -EIO;
+	}
+
 	if (ei->start_clu == EXFAT_FREE_CLUSTER) {
 		exfat_fs_error(sb,
 			       "non-zero size file starts with zero cluster (size : %llu, p_dir : %u, entry : 0x%08x)",

fs/exfat/super.c

@@ -629,6 +629,17 @@ static int __exfat_fill_super(struct super_block *sb,
 		goto free_bh;
 	}
 
+	if (!exfat_test_bitmap(sb, sbi->root_dir)) {
+		exfat_warn(sb, "failed to test first cluster bit of root dir(%u)",
+			   sbi->root_dir);
+		/*
+		 * The first cluster bit of the root directory should never
+		 * be unset except when storage is corrupted. This bit is
+		 * set to allow operations after mount.
+		 */
+		exfat_set_bitmap(sb, sbi->root_dir, false);
+	}
+
 	ret = exfat_count_used_clusters(sb, &sbi->used_clusters);
 	if (ret) {
 		exfat_err(sb, "failed to scan clusters");
@@ -813,10 +824,21 @@ static int exfat_init_fs_context(struct fs_context *fc)
 	ratelimit_state_init(&sbi->ratelimit, DEFAULT_RATELIMIT_INTERVAL,
 			DEFAULT_RATELIMIT_BURST);
 
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE && fc->root) {
+		struct super_block *sb = fc->root->d_sb;
+		struct exfat_mount_options *cur_opts = &EXFAT_SB(sb)->options;
+
+		sbi->options.fs_uid = cur_opts->fs_uid;
+		sbi->options.fs_gid = cur_opts->fs_gid;
+		sbi->options.fs_fmask = cur_opts->fs_fmask;
+		sbi->options.fs_dmask = cur_opts->fs_dmask;
+	} else {
 		sbi->options.fs_uid = current_uid();
 		sbi->options.fs_gid = current_gid();
 		sbi->options.fs_fmask = current->fs->umask;
 		sbi->options.fs_dmask = current->fs->umask;
+	}
+
 	sbi->options.allow_utime = -1;
 	sbi->options.errors = EXFAT_ERRORS_RO;
 	exfat_set_iocharset(&sbi->options, exfat_default_iocharset);