stable inclusion
from stable-5.10.65
commit a7d0a59e21efef97d6499b2ce387711edb206cb0
bugzilla: 182361 https://gitee.com/openeuler/kernel/issues/I4EH3U

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a7d0a59e21efef97d6499b2ce387711edb206cb0

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

[ Upstream commit 525e2f9f ]

st->bucket stores the current bucket number.
st->offset stores the offset within this bucket that is the sk to be
seq_show().  Thus, st->offset only makes sense within the same
st->bucket.

These two variables are an optimization for the common no-lseek case.
When resuming the seq_file iteration (i.e. seq_start()),
tcp_seek_last_pos() tries to continue from the st->offset
at bucket st->bucket.

However, it is possible that the bucket pointed by st->bucket
has changed and st->offset may end up skipping the whole st->bucket
without finding a sk.  In this case, tcp_seek_last_pos() currently
continues to satisfy the offset condition in the next (and incorrect)
bucket.  Instead, regardless of the offset value, the first sk of the
next bucket should be returned.  Thus, "bucket == st->bucket" check is
added to tcp_seek_last_pos().

The chance of hitting this is small and the issue is a decade old,
so targeting for the next tree.

Fixes: a8b690f9 ("tcp: Fix slowness in read /proc/net/tcp")
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: NEric Dumazet <edumazet@google.com>
Acked-by: NKuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: NYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210701200541.1033917-1-kafai@fb.comSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>