linux-ext4 - [PATCH 2/2] ext4: fix out-of-bound read in ext4_xattr_inode_dec_ref

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Message-ID: <20250126082731.2037385-3-yebin10@huawei.com>
Date: Sun, 26 Jan 2025 16:27:31 +0800
From: Ye Bin <yebin10@...wei.com>
To: <tytso@....edu>, <adilger.kernel@...ger.ca>, <linux-ext4@...r.kernel.org>
CC: <jack@...e.cz>, <zhangxiaoxu5@...wei.com>
Subject: [PATCH 2/2] ext4: fix out-of-bound read in ext4_xattr_inode_dec_ref_all()

There's issue as follows:
BUG: KASAN: use-after-free in ext4_xattr_inode_dec_ref_all+0x6ff/0x790
Read of size 4 at addr ffff88807b003000 by task syz-executor.0/15172

CPU: 3 PID: 15172 Comm: syz-executor.0
Call Trace:
 __dump_stack lib/dump_stack.c:82 [inline]
 dump_stack+0xbe/0xfd lib/dump_stack.c:123
 print_address_description.constprop.0+0x1e/0x280 mm/kasan/report.c:400
 __kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560
 kasan_report+0x3a/0x50 mm/kasan/report.c:585
 ext4_xattr_inode_dec_ref_all+0x6ff/0x790 fs/ext4/xattr.c:1137
 ext4_xattr_delete_inode+0x4c7/0xda0 fs/ext4/xattr.c:2896
 ext4_evict_inode+0xb3b/0x1670 fs/ext4/inode.c:323
 evict+0x39f/0x880 fs/inode.c:622
 iput_final fs/inode.c:1746 [inline]
 iput fs/inode.c:1772 [inline]
 iput+0x525/0x6c0 fs/inode.c:1758
 ext4_orphan_cleanup fs/ext4/super.c:3298 [inline]
 ext4_fill_super+0x8c57/0xba40 fs/ext4/super.c:5300
 mount_bdev+0x355/0x410 fs/super.c:1446
 legacy_get_tree+0xfe/0x220 fs/fs_context.c:611
 vfs_get_tree+0x8d/0x2f0 fs/super.c:1576
 do_new_mount fs/namespace.c:2983 [inline]
 path_mount+0x119a/0x1ad0 fs/namespace.c:3316
 do_mount+0xfc/0x110 fs/namespace.c:3329
 __do_sys_mount fs/namespace.c:3540 [inline]
 __se_sys_mount+0x219/0x2e0 fs/namespace.c:3514
 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x67/0xd1

Memory state around the buggy address:
 ffff88807b002f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88807b002f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807b003000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88807b003080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807b003100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Above issue happens as ext4_xattr_delete_inode() isn't check xattr
is valid if xattr is in inode.
To solve above issue call xattr_check_inode() check if xattr if valid
in inode.

Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
Signed-off-by: Ye Bin <yebin10@...wei.com>
---
 fs/ext4/xattr.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 0e4494863d15..cb724477f8da 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2922,7 +2922,6 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
 			    int extra_credits)
 {
 	struct buffer_head *bh = NULL;
-	struct ext4_xattr_ibody_header *header;
 	struct ext4_iloc iloc = { .bh = NULL };
 	struct ext4_xattr_entry *entry;
 	struct inode *ea_inode;
@@ -2937,6 +2936,9 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
 
 	if (ext4_has_feature_ea_inode(inode->i_sb) &&
 	    ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
+		struct ext4_xattr_ibody_header *header;
+		struct ext4_inode *raw_inode;
+		void *end;
 
 		error = ext4_get_inode_loc(inode, &iloc);
 		if (error) {
@@ -2952,14 +2954,20 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
 			goto cleanup;
 		}
 
-		header = IHDR(inode, ext4_raw_inode(&iloc));
-		if (header->h_magic == cpu_to_le32(EXT4_XATTR_MAGIC))
+		raw_inode = ext4_raw_inode(&iloc);
+		header = IHDR(inode, raw_inode);
+		end = ITAIL(inode, raw_inode);
+		if (header->h_magic == cpu_to_le32(EXT4_XATTR_MAGIC)) {
+			error = xattr_check_inode(inode, header, end);
+			if (error)
+				goto cleanup;
 			ext4_xattr_inode_dec_ref_all(handle, inode, iloc.bh,
 						     IFIRST(header),
 						     false /* block_csum */,
 						     ea_inode_array,
 						     extra_credits,
 						     false /* skip_quota */);
+		}
 	}
 
 	if (EXT4_I(inode)->i_file_acl) {
-- 
2.34.1