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SubjectRe: libceph: follow redirect replies from osds
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On Fri, 2020-02-28 at 12:46 +0000, Colin Ian King wrote:
> Hi,
>
> Static analysis with Coverity has detected a potential issue in the
> following commit in function ceph_redirect_decode():
>
> commit 205ee1187a671c3b067d7f1e974903b44036f270
> Author: Ilya Dryomov <ilya.dryomov@inktank.com>
> Date: Mon Jan 27 17:40:20 2014 +0200
>
> libceph: follow redirect replies from osds
>
> The issue is as follows:
>
>
> 3486 len = ceph_decode_32(p);
>
> Unused value (UNUSED_VALUE)
> assigned_pointer: Assigning value from len to *p here, but that stored
> value is overwritten before it can be used.
>
> 3487 *p += len; /* skip osd_instructions */
> 3488
> 3489 /* skip the rest */
>
> value_overwrite: Overwriting previous write to *p with value from
> struct_end.
>
> 3490 *p = struct_end;
>
> The *p assignment in line 3487 is effectively being overwritten by the
> *p assignment in 3490. Maybe the following is correct:
>
> len = ceph_decode_32(p);
> - p += len; /* skip osd_instructions */
> + struct_end = *p + len; /* skip osd_instructions */
>
> /* skip the rest */
> *p = struct_end;
>
> I'm not familiar with the ceph structure here, so I'm not sure what the
> correct fix would be.
>

Probably something like this? (untested, of course)

----------------------

[PATCH] libceph: fix up Coverity warning in ceph_redirect_decode

We're going to skip to the end of the msg after checking the
object_name anyway, so there is no need to separately decode
the osd instructions that follow it.

Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
net/ceph/osd_client.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 8ff2856e2d52..51810db4130a 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -3483,9 +3483,6 @@ static int ceph_redirect_decode(void **p, void
*end,
goto e_inval;
}

- len = ceph_decode_32(p);
- *p += len; /* skip osd_instructions */
-
/* skip the rest */
*p = struct_end;
out:
--
2.24.1



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