From: Vasily Averin <vvs@xxxxxxxxxxxxx> [ Upstream commit db8dd9697238be70a6b4f9d0284cd89f59c0e070 ] if seq_file .next fuction does not change position index, read after some lseek can generate unexpected output. # mount | grep cgroup # dd if=/mnt/cgroup.procs bs=1 # normal output ... 1294 1295 1296 1304 1382 584+0 records in 584+0 records out 584 bytes copied dd: /mnt/cgroup.procs: cannot skip to specified offset 83 <<< generates end of last line 1383 <<< ... and whole last line once again 0+1 records in 0+1 records out 8 bytes copied dd: /mnt/cgroup.procs: cannot skip to specified offset 1386 <<< generates last line anyway 0+1 records in 0+1 records out 5 bytes copied https://bugzilla.kernel.org/show_bug.cgi?id=206283 Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/cgroup/cgroup-v1.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 51063e7a93c28..c9628b9a41d23 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -501,6 +501,7 @@ static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos) */ p++; if (p >= end) { + (*pos)++; return NULL; } else { *pos = *p; -- 2.20.1
