2016-10-13 15:16:57

by Geert Uytterhoeven

Subject: [PATCH] ceph: Fix uninitialized dentry pointer in ceph_real_mount()

fs/ceph/super.c: In function ‘ceph_real_mount’:
fs/ceph/super.c:818: warning: ‘root’ may be used uninitialized in this function

If s_root is already valid, dentry pointer root is never initialized,
and returned by ceph_real_mount(). This will cause a crash later when
the caller dereferences the pointer.

Fix this by initializing root early.

Fixes: ce2728aaa82bbeba ("ceph: avoid accessing / when mounting a subpath")
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
Compile-tested only.
---
fs/ceph/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index a29ffce981879d5f..794c5fd0e0cf5e45 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -821,7 +821,8 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
dout("mount start %p\n", fsc);
mutex_lock(&fsc->client->mount_mutex);

- if (!fsc->sb->s_root) {
+ root = fsc->sb->s_root;
+ if (!root) {
const char *path;
err = __ceph_open_session(fsc->client, started);
if (err < 0)
--
1.9.1

2016-10-14 02:48:00

by Yan, Zheng

Subject: Re: [PATCH] ceph: Fix uninitialized dentry pointer in ceph_real_mount()

On Thu, Oct 13, 2016 at 11:15 PM, Geert Uytterhoeven
<[email protected]> wrote:
> fs/ceph/super.c: In function ‘ceph_real_mount’:
> fs/ceph/super.c:818: warning: ‘root’ may be used uninitialized in this function
>
> If s_root is already valid, dentry pointer root is never initialized,
> and returned by ceph_real_mount(). This will cause a crash later when
> the caller dereferences the pointer.
>
> Fix this by initializing root early.
>
> Fixes: ce2728aaa82bbeba ("ceph: avoid accessing / when mounting a subpath")
> Signed-off-by: Geert Uytterhoeven <[email protected]>
> ---
> Compile-tested only.
> ---
> fs/ceph/super.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index a29ffce981879d5f..794c5fd0e0cf5e45 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -821,7 +821,8 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
> dout("mount start %p\n", fsc);
> mutex_lock(&fsc->client->mount_mutex);
>
> - if (!fsc->sb->s_root) {
> + root = fsc->sb->s_root;
> + if (!root) {
> const char *path;
> err = __ceph_open_session(fsc->client, started);
> if (err < 0)

For sb->s_root is not NULL case, we also need to increase sb->s_root's
reference count. I applied this patch and fixed it.

Regards
Yan, Zheng


> --
> 1.9.1
>

2016-10-17 07:46:24

by Geert Uytterhoeven

Subject: Re: [PATCH] ceph: Fix uninitialized dentry pointer in ceph_real_mount()

Hi Zheng,

On Fri, Oct 14, 2016 at 4:47 AM, Yan, Zheng <[email protected]> wrote:
> On Thu, Oct 13, 2016 at 11:15 PM, Geert Uytterhoeven
> <[email protected]> wrote:
>> fs/ceph/super.c: In function ‘ceph_real_mount’:
>> fs/ceph/super.c:818: warning: ‘root’ may be used uninitialized in this function
>>
>> If s_root is already valid, dentry pointer root is never initialized,
>> and returned by ceph_real_mount(). This will cause a crash later when
>> the caller dereferences the pointer.
>>
>> Fix this by initializing root early.
>>
>> Fixes: ce2728aaa82bbeba ("ceph: avoid accessing / when mounting a subpath")
>> Signed-off-by: Geert Uytterhoeven <[email protected]>
>> ---
>> Compile-tested only.
>> ---
>> fs/ceph/super.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
>> index a29ffce981879d5f..794c5fd0e0cf5e45 100644
>> --- a/fs/ceph/super.c
>> +++ b/fs/ceph/super.c
>> @@ -821,7 +821,8 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>> dout("mount start %p\n", fsc);
>> mutex_lock(&fsc->client->mount_mutex);
>>
>> - if (!fsc->sb->s_root) {
>> + root = fsc->sb->s_root;
>> + if (!root) {
>> const char *path;
>> err = __ceph_open_session(fsc->client, started);
>> if (err < 0)
>
> For sb->s_root is not NULL case, we also need to increase sb->s_root's
> reference count.

OK

> I applied this patch and fixed it.

Thanks for handling!

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds