[PATCH] gfs2: validate stuffed inode size before unstuffing

[Jiaming Zhang <r772577952@gmail.com>]

A corrupted GFS2 image can store a dinode size that is larger than what VFS
i_size can represent. gfs2_dinode_in() reads the on-disk di_size as a u64 and
writes it directly into inode->i_size. If the value is larger than S64_MAX, the
incore i_size becomes negative. That negative value can bypass the existing
stuffed inode size check:

inode->i_size > gfs2_max_stuffed_size(ip)

Later, gfs2_quotad may try to sync the quota file and unstuff the quota inode.
gfs2_unstuffer_folio() reads the negative i_size into an unsigned length and
passes it to memcpy(), turning it into a huge copy size and triggering a
out-of-bound issue.

Reject dinodes whose size exceeds sb->s_maxbytes before storing the value in
inode->i_size. Also make the stuffed inode check use the raw on-disk size while
it is still unsigned. As a defensive measure, validate the incore i_size again
before unstuffing and pass the checked size down to gfs2_unstuffer_folio().

Fixes: 70376c7ff312 ("gfs2: Always check inode size of inline inodes")
Closes: https://lore.kernel.org/lkml/CANypQFaF6bvORKKbRALvEL0k_epFaneFiOQqco4gjdmKVbdURg@mail.gmail.com/
Assisted-by: Codex:gpt-5.5-xhigh
Cc: stable@vger.kernel.org
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
---
 fs/gfs2/bmap.c  | 18 ++++++++++++------
 fs/gfs2/glops.c | 10 +++++++---
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 51ac1fd44f78..89c46c1d622c 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -52,16 +52,15 @@ static int punch_hole(struct gfs2_inode *ip, u64 offset, u64 length);
  * Returns: errno
  */
 static int gfs2_unstuffer_folio(struct gfs2_inode *ip, struct buffer_head *dibh,
-			       u64 block, struct folio *folio)
+			       u64 block, struct folio *folio, size_t size)
 {
 	struct inode *inode = &ip->i_inode;
 
 	if (!folio_test_uptodate(folio)) {
 		void *kaddr = kmap_local_folio(folio, 0);
-		u64 dsize = i_size_read(inode);
- 
-		memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
-		memset(kaddr + dsize, 0, folio_size(folio) - dsize);
+
+		memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), size);
+		memset(kaddr + size, 0, folio_size(folio) - size);
 		kunmap_local(kaddr);
 
 		folio_mark_uptodate(folio);
@@ -92,9 +91,15 @@ static int __gfs2_unstuff_inode(struct gfs2_inode *ip, struct folio *folio)
 	struct buffer_head *bh, *dibh;
 	struct gfs2_dinode *di;
 	u64 block = 0;
+	loff_t size = i_size_read(&ip->i_inode);
 	int isdir = gfs2_is_dir(ip);
 	int error;
 
+	if (unlikely(size < 0 || size > gfs2_max_stuffed_size(ip))) {
+		gfs2_consist_inode(ip);
+		return -EIO;
+	}
+
 	error = gfs2_meta_inode_buffer(ip, &dibh);
 	if (error)
 		return error;
@@ -116,7 +121,8 @@ static int __gfs2_unstuff_inode(struct gfs2_inode *ip, struct folio *folio)
 					      dibh, sizeof(struct gfs2_dinode));
 			brelse(bh);
 		} else {
-			error = gfs2_unstuffer_folio(ip, dibh, block, folio);
+			error = gfs2_unstuffer_folio(ip, dibh, block, folio,
+						     size);
 			if (error)
 				goto out_brelse;
 		}
diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c
index 28f32424ee64..33575fa681f5 100644
--- a/fs/gfs2/glops.c
+++ b/fs/gfs2/glops.c
@@ -393,11 +393,16 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 	umode_t mode = be32_to_cpu(str->di_mode);
 	struct inode *inode = &ip->i_inode;
 	bool is_new = inode_state_read_once(inode) & I_NEW;
+	u64 size = be64_to_cpu(str->di_size);
 
 	if (unlikely(ip->i_no_addr != be64_to_cpu(str->di_num.no_addr))) {
 		gfs2_consist_inode(ip);
 		return -EIO;
 	}
+	if (unlikely(size > (u64)inode->i_sb->s_maxbytes)) {
+		gfs2_consist_inode(ip);
+		return -EIO;
+	}
 	if (unlikely(!is_new && inode_wrong_type(inode, mode))) {
 		gfs2_consist_inode(ip);
 		return -EIO;
@@ -418,7 +423,7 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 	i_uid_write(inode, be32_to_cpu(str->di_uid));
 	i_gid_write(inode, be32_to_cpu(str->di_gid));
 	set_nlink(inode, be32_to_cpu(str->di_nlink));
-	i_size_write(inode, be64_to_cpu(str->di_size));
+	i_size_write(inode, size);
 	gfs2_set_inode_blocks(inode, be64_to_cpu(str->di_blocks));
 	atime.tv_sec = be64_to_cpu(str->di_atime);
 	atime.tv_nsec = be32_to_cpu(str->di_atime_nsec);
@@ -462,7 +467,7 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 		return -EIO;
 	}
 
-	if (gfs2_is_stuffed(ip) && inode->i_size > gfs2_max_stuffed_size(ip)) {
+	if (gfs2_is_stuffed(ip) && size > gfs2_max_stuffed_size(ip)) {
 		gfs2_consist_inode(ip);
 		return -EIO;
 	}
@@ -707,4 +712,3 @@ const struct gfs2_glock_operations *gfs2_glops_list[] = {
 	[LM_TYPE_QUOTA] = &gfs2_quota_glops,
 	[LM_TYPE_JOURNAL] = &gfs2_journal_glops,
 };
-
-- 
2.43.0