linux-kernel - [PATCH 7/7] sysvipc_find_ipc should increase position index

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Date:   Fri, 24 Jan 2020 10:03:12 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        NeilBrown <neilb@...e.com>, Waiman Long <longman@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>
Subject: [PATCH 7/7] sysvipc_find_ipc should increase position index

if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 ipc/util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ipc/util.c b/ipc/util.c
index 915eacb..7a3ab2e 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -764,13 +764,13 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 			total++;
 	}
 
+	*new_pos = pos + 1;
 	if (total >= ids->in_use)
 		return NULL;
 
 	for (; pos < ipc_mni; pos++) {
 		ipc = idr_find(&ids->ipcs_idr, pos);
 		if (ipc != NULL) {
-			*new_pos = pos + 1;
 			rcu_read_lock();
 			ipc_lock_object(ipc);
 			return ipc;
-- 
1.8.3.1