From: Zhihao Cheng chengzhihao1@huawei.com
stable inclusion from stable-v5.10.210 commit d132010e6d5c0cb2e28ce9e91ab3ad0ad4cd1063 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9L5M6 CVE: CVE-2024-26972
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 1e022216dcd248326a5bb95609d12a6815bca4e2 upstream.
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@vger.kernel.org Fixes: 2c58d548f570 ("fscrypt: cache decrypted symlink target in ->i_link") Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Suggested-by: Eric Biggers ebiggers@kernel.org Reviewed-by: Eric Biggers ebiggers@google.com Signed-off-by: Richard Weinberger richard@nod.at Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: ZhaoLong Wang wangzhaolong1@huawei.com --- fs/ubifs/dir.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c index 1686e7aea823..9bfa0b6b3771 100644 --- a/fs/ubifs/dir.c +++ b/fs/ubifs/dir.c @@ -1126,6 +1126,8 @@ static int ubifs_mknod(struct inode *dir, struct dentry *dentry, 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: