From 1e5654de0f51890f88abd409ebf4867782431e81 Mon Sep 17 00:00:00 2001

From: Namjae Jeon <namjae.jeon@samsung.com>

Date: Fri, 11 Jun 2021 09:40:24 +0900

Subject: [Backport 1e5654de0f51] exfat: handle wrong stream entry size in

 exfat_readdir()

The compatibility issue between linux exfat and exfat of some camera

company was reported from Florian. In their exfat, if the number of files

exceeds any limit, the DataLength in stream entry of the directory is

no longer updated. So some files created from camera does not show in

linux exfat. because linux exfat doesn't allow that cpos becomes larger

than DataLength of stream entry. This patch check DataLength in stream

entry only if the type is ALLOC_NO_FAT_CHAIN and add the check ensure

that dentry offset does not exceed max dentries size(256 MB) to avoid

the circular FAT chain issue.

Fixes: ca06197382bd ("exfat: add directory operations")

Cc: stable@vger.kernel.org # v5.9

Reported-by: Florian Cramer <flrncrmr@gmail.com>

Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>

Tested-by: Chris Down <chris@chrisdown.name>

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

---

 src/dir.c | 8 +++++---

 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/dir.c b/src/dir.c

index c4523648472a088a2477ea9c3ffe7416c498b523..cb1c0d8c17141b1a0b1fdb70167cce3ec3c5446b 100644

--- a/src/dir.c

+++ b/src/dir.c

@@ -63,7 +63,7 @@ static void exfat_get_uniname_from_ext_entry(struct super_block *sb,

 static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_entry *dir_entry)

 {

 	int i, dentries_per_clu, dentries_per_clu_bits = 0, num_ext;

-	unsigned int type, clu_offset;

+	unsigned int type, clu_offset, max_dentries;

 	sector_t sector;

 	struct exfat_chain dir, clu;

 	struct exfat_uni_name uni_name;

@@ -86,6 +86,8 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent

 	dentries_per_clu = sbi->dentries_per_clu;

 	dentries_per_clu_bits = ilog2(dentries_per_clu);

+	max_dentries = (unsigned int)min_t(u64, MAX_EXFAT_DENTRIES,

+					   (u64)sbi->num_clusters << dentries_per_clu_bits);

 	clu_offset = dentry >> dentries_per_clu_bits;

 	exfat_chain_dup(&clu, &dir;;

@@ -109,7 +111,7 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent

 		}

 	}

-	while (clu.dir != EXFAT_EOF_CLUSTER) {

+	while (clu.dir != EXFAT_EOF_CLUSTER && dentry < max_dentries) {

 		i = dentry & (dentries_per_clu - 1);

 		for ( ; i < dentries_per_clu; i++, dentry++) {

@@ -245,7 +247,7 @@ static int exfat_iterate(struct file *filp, struct dir_context *ctx)

 	if (err)

 		goto unlock;

 get_new:

-	if (cpos >= i_size_read(inode))

+	if (ei->flags == ALLOC_NO_FAT_CHAIN && cpos >= i_size_read(inode))

 		goto end_of_dir;

 	err = exfat_readdir(inode, &cpos, &de);

-- 

2.31.1