Re: [syzbot] Re: kernel BUG in ext4_write_inline_data()

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Subject: Re: kernel BUG in ext4_write_inline_data()
Author: dmantipov@xxxxxxxxx

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 43fb83c17ba2d63dfb798f0be7453ed55ca3f9c2

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 74f2071189b2..759a0d69b277 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3558,6 +3558,12 @@ extern int ext4_get_max_inline_size(struct inode *inode);
 extern int ext4_find_inline_data_nolock(struct inode *inode);
 extern int ext4_destroy_inline_data(handle_t *handle, struct inode *inode);
 
+static inline bool ext4_inline_possible(struct inode *inode,
+					loff_t pos, unsigned len)
+{
+	return pos + len <= ext4_get_max_inline_size(inode);
+}
+
 int ext4_readpage_inline(struct inode *inode, struct folio *folio);
 extern int ext4_try_to_write_inline_data(struct address_space *mapping,
 					 struct inode *inode,
diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index 3536ca7e4fcc..ec25f066a2c2 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -668,7 +668,7 @@ int ext4_try_to_write_inline_data(struct address_space *mapping,
 	struct folio *folio;
 	struct ext4_iloc iloc;
 
-	if (pos + len > ext4_get_max_inline_size(inode))
+	if (!ext4_inline_possible(inode, pos, len))
 		goto convert;
 
 	ret = ext4_get_inode_loc(inode, &iloc);
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 89aade6f45f6..9fe49571bc93 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3076,7 +3076,8 @@ static int ext4_da_write_end(struct file *file,
 
 	if (write_mode != CONVERT_INLINE_DATA &&
 	    ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA) &&
-	    ext4_has_inline_data(inode))
+	    ext4_has_inline_data(inode) &&
+	    ext4_inline_possible(inode, pos, len))
 		return ext4_write_inline_data_end(inode, pos, len, copied,
 						  folio);