Skip to contentSkip to conversation

FAILED: patch "[PATCH] f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode" failed to apply to 6.1-stable tree

PATCH [email protected] 1 participant 1 message Jul 2

Subsystems (2)
Stable branch F2FS file system
lore
Share & tools
lore

[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x e0288584baa5dc41df4a829a023c4c1b33fe53d7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026070243-overload-marina-0abd@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e0288584baa5dc41df4a829a023c4c1b33fe53d7 Mon Sep 17 00:00:00 2001
From: Chao Yu <[email protected]>
Date: Thu, 21 May 2026 10:15:05 +0800
Subject: [PATCH] f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode

- ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE) - shrink
- f2fs_gc
- gc_data_segment
- ra_data_block(cow_inode)
- mapping = F2FS_I(inode)->atomic_inode->i_mapping
: f2fs_is_cow_file(cow_inode) is true
- f2fs_evict_inode(atomic_inode)
- clear_inode_flag(fi->cow_inode, FI_COW_FILE)
- F2FS_I(fi->cow_inode)->atomic_inode = NULL
...
- truncate_inode_pages_final(atomic_inode)
- f2fs_grab_cache_folio(mapping)
: create folio in atomic_inode->mapping
- clear_inode(atomic_inode)
- BUG_ON(atomic_inode->i_data.nrpages)

We need to add a reference on fi->atomic_inode before using its mapping field during garbage collection, otherwise, it will cause UAF issue.

Cc [email protected]
Cc Daeho Jeong <[email protected]>
Cc Sunmin Jeong <[email protected]>
Fixes 3db1de0e582c ("f2fs: change the current atomic write way")
Fixes f18d00769336 ("f2fs: use meta inode for GC of COW file")
Signed-off-by Chao Yu <[email protected]>
Signed-off-by Jaegeuk Kim <[email protected]>
fs/f2fs/gc.c +42 -8
index 99bc59889825..69e0a867219d 100644
@@ -1220,8 +1220,8 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 static int ra_data_block(struct inode *inode, pgoff_t index)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	struct address_space *mapping = f2fs_is_cow_file(inode) ?
-				F2FS_I(inode)->atomic_inode->i_mapping : inode->i_mapping;
+	struct address_space *mapping = inode->i_mapping;
+	struct inode *atomic_inode = NULL;
 	struct dnode_of_data dn;
 	struct folio *folio, *efolio;
 	struct f2fs_io_info fio = {

@@ -1236,9 +1236,22 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
 	};
 	int err = 0;
 
+	f2fs_down_read(&F2FS_I(inode)->i_sem);
+	if (f2fs_is_cow_file(inode)) {
+		atomic_inode = igrab(F2FS_I(inode)->atomic_inode);
+		if (!atomic_inode) {
+			f2fs_up_read(&F2FS_I(inode)->i_sem);
+			return -EBUSY;
+		}
+		mapping = atomic_inode->i_mapping;
+	}
+	f2fs_up_read(&F2FS_I(inode)->i_sem);
+
 	folio = f2fs_grab_cache_folio(mapping, index, true);
-	if (IS_ERR(folio))
-		return PTR_ERR(folio);
+	if (IS_ERR(folio)) {
+		err = PTR_ERR(folio);
+		goto out_iput;
+	}
 
 	if (f2fs_lookup_read_extent_cache_block(inode, index,
 						&dn.data_blkaddr)) {

@@ -1299,11 +1312,16 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
 	f2fs_update_iostat(sbi, inode, FS_DATA_READ_IO, F2FS_BLKSIZE);
 	f2fs_update_iostat(sbi, NULL, FS_GDATA_READ_IO, F2FS_BLKSIZE);
 
+	if (atomic_inode)
+		iput(atomic_inode);
 	return 0;
 put_encrypted_page:
 	f2fs_put_page(fio.encrypted_page, true);
 put_folio:
 	f2fs_folio_put(folio, true);
+out_iput:
+	if (atomic_inode)
+		iput(atomic_inode);
 	return err;
 }
 

@@ -1314,8 +1332,8 @@ static int ra_data_block(struct inode *inode, pgoff_t index)
 static int move_data_block(struct inode *inode, block_t bidx,
 				int gc_type, unsigned int segno, int off)
 {
-	struct address_space *mapping = f2fs_is_cow_file(inode) ?
-				F2FS_I(inode)->atomic_inode->i_mapping : inode->i_mapping;
+	struct address_space *mapping = inode->i_mapping;
+	struct inode *atomic_inode = NULL;
 	struct f2fs_io_info fio = {
 		.sbi = F2FS_I_SB(inode),
 		.ino = inode->i_ino,

@@ -1337,10 +1355,23 @@ static int move_data_block(struct inode *inode, block_t bidx,
 				(fio.sbi->gc_mode != GC_URGENT_HIGH) ?
 				CURSEG_ALL_DATA_ATGC : CURSEG_COLD_DATA;
 
+	f2fs_down_read(&F2FS_I(inode)->i_sem);
+	if (f2fs_is_cow_file(inode)) {
+		atomic_inode = igrab(F2FS_I(inode)->atomic_inode);
+		if (!atomic_inode) {
+			f2fs_up_read(&F2FS_I(inode)->i_sem);
+			return -EBUSY;
+		}
+		mapping = atomic_inode->i_mapping;
+	}
+	f2fs_up_read(&F2FS_I(inode)->i_sem);
+
 	/* do not read out */
 	folio = f2fs_grab_cache_folio(mapping, bidx, false);
-	if (IS_ERR(folio))
-		return PTR_ERR(folio);
+	if (IS_ERR(folio)) {
+		err = PTR_ERR(folio);
+		goto out_iput;
+	}
 
 	if (!check_valid_map(F2FS_I_SB(inode), segno, off)) {
 		err = -ENOENT;

@@ -1473,6 +1504,9 @@ static int move_data_block(struct inode *inode, block_t bidx,
 	folio_unlock(folio);
 	folio_end_dropbehind(folio);
 	folio_put(folio);
+out_iput:
+	if (atomic_inode)
+		iput(atomic_inode);
 	return err;
 }
fs/f2fs/inode.c +8 -3
index 1694726122e6..939d75663a40 100644
@@ -863,10 +863,15 @@ void f2fs_evict_inode(struct inode *inode)
 	f2fs_abort_atomic_write(inode, true);
 
 	if (fi->cow_inode && f2fs_is_cow_file(fi->cow_inode)) {
-		clear_inode_flag(fi->cow_inode, FI_COW_FILE);
-		F2FS_I(fi->cow_inode)->atomic_inode = NULL;
-		iput(fi->cow_inode);
+		struct inode *cow_inode = fi->cow_inode;
+
+		f2fs_down_write(&F2FS_I(cow_inode)->i_sem);
+		clear_inode_flag(cow_inode, FI_COW_FILE);
+		F2FS_I(cow_inode)->atomic_inode = NULL;
 		fi->cow_inode = NULL;
+		f2fs_up_write(&F2FS_I(cow_inode)->i_sem);
+
+		iput(cow_inode);
 	}
 
 	trace_f2fs_evict_inode(inode);