On Fri, Dec 22, 2023 at 04:54:46PM +0800, Zhihao Cheng wrote: > 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: [email protected] > Fixes: 2c58d548f570 ("fscrypt: cache decrypted symlink target in ->i_link") > Signed-off-by: Zhihao Cheng <[email protected]> > Suggested-by: Eric Biggers <[email protected]> > --- > fs/ubifs/dir.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c > index 3b13c648d490..e413a9cf8ee3 100644 > --- a/fs/ubifs/dir.c > +++ b/fs/ubifs/dir.c > @@ -1234,6 +1234,8 @@ static int ubifs_symlink(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:
Reviewed-by: Eric Biggers <[email protected]> - Eric
