| Message ID | 20231222025025.2940450-3-chengzhihao1@huawei.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | ubifs: Fix two kmemleaks in error path | expand |
On Fri, Dec 22, 2023 at 10:50:25AM +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. > > Fixes: 2c58d548f570 ("fscrypt: cache decrypted symlink target in ->i_link") > Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> > --- > fs/ubifs/dir.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c > index 3b13c648d490..9baf029416d4 100644 > --- a/fs/ubifs/dir.c > +++ b/fs/ubifs/dir.c > @@ -1234,6 +1234,9 @@ 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. */ > + if (IS_ENCRYPTED(inode)) > + fscrypt_free_inode(inode); > make_bad_inode(inode); > iput(inode); > out_fname: fscrypt_free_inode() should be called unconditionally, because fscrypt_free_inode() already checks for IS_ENCRYPTED(). Also, please add 'Cc: stable@vger.kernel.org' to your commit message. Also, please add linux-fscrypt@vger.kernel.org to the recipients of this patch. Anyway, thanks for catching this bug! It's annoying that make_bad_inode() changes the inode's type from a symlink to a regular file; normally an inode's type can never change. Your fix looks fine, though. Thanks! - Eric
在 2023/12/22 14:22, Eric Biggers 写道: > fscrypt_free_inode() should be called unconditionally, because > fscrypt_free_inode() already checks for IS_ENCRYPTED(). > > Also, please add 'Cc:stable@vger.kernel.org' to your commit message. > > Also, please addlinux-fscrypt@vger.kernel.org to the recipients of this patch. > > Anyway, thanks for catching this bug! It's annoying that make_bad_inode() > changes the inode's type from a symlink to a regular file; normally an inode's > type can never change. Your fix looks fine, though. Thanks! Thanks for suggestions, I will modify them in v2.
diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c index 3b13c648d490..9baf029416d4 100644 --- a/fs/ubifs/dir.c +++ b/fs/ubifs/dir.c @@ -1234,6 +1234,9 @@ 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. */ + if (IS_ENCRYPTED(inode)) + fscrypt_free_inode(inode); make_bad_inode(inode); iput(inode); out_fname:
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. Fixes: 2c58d548f570 ("fscrypt: cache decrypted symlink target in ->i_link") Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> --- fs/ubifs/dir.c | 3 +++ 1 file changed, 3 insertions(+)