From: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
[ Upstream commit 6379b44cdcd67f5f5d986b73953e99700591edfa ]
For error handling path in ubifs_symlink(), inode will be marked as
bad first, then iput() is invoked. If inode->i_link is initialized by
fscrypt_encrypt_symlink() in encryption scenario, inode->i_link won't
be freed by callchain ubifs_free_inode -> fscrypt_free_inode in error
handling path, because make_bad_inode() has changed 'inode->i_mode' as
'S_IFREG'.
Following kmemleak is easy to be reproduced by injecting error in
ubifs_jnl_update() when doing symlink in encryption scenario:
unreferenced object 0xffff888103da3d98 (size 8):
comm "ln", pid 1692, jiffies 4294914701 (age 12.045s)
backtrace:
kmemdup+0x32/0x70
__fscrypt_encrypt_symlink+0xed/0x1c0
ubifs_symlink+0x210/0x300 [ubifs]
vfs_symlink+0x216/0x360
do_symlinkat+0x11a/0x190
do_syscall_64+0x3b/0xe0
There are two ways fixing it:
1. Remove make_bad_inode() in error handling path. We can do that
because ubifs_evict_inode() will do same processes for good
symlink inode and bad symlink inode, for inode->i_nlink checking
is before is_bad_inode().
2. Free inode->i_link before marking inode bad.
Method 2 is picked, it has less influence, personally, I think.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 2c58d548f570 ("fscrypt: cache decrypted symlink target in ->i_link")
Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Suggested-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Reviewed-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
(cherry picked from commit 6379b44cdcd67f5f5d986b73953e99700591edfa)
[Vegard: CVE-2024-26972; no conflicts]
Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
---
fs/ubifs/dir.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index be45972ff95d9..d2b76367908f2 100644
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -1126,6 +1126,8 @@ static int ubifs_mknod(struct mnt_idmap *idmap, struct inode *dir,
dir_ui->ui_size = dir->i_size;
mutex_unlock(&dir_ui->ui_mutex);
out_inode:
+ /* Free inode->i_link before inode is marked as bad. */
+ fscrypt_free_inode(inode);
make_bad_inode(inode);
iput(inode);
out_fname:
--
2.34.1
