[PATCH 5.10.y 1/3] proc: use generic setattr() for /proc/$PID/net

[Sasha Levin <sashal@kernel.org>]

From: Thomas Weißschuh <linux@weissschuh.net>

[ Upstream commit 18e66ae67673f2c8df6f02428798b1355691f2a9 ]

All other files in /proc/$PID/ use proc_setattr().

Not using it allows the usage of chmod() on /proc/$PID/net, even on
other processes owned by the same user.
The same would probably also be true for other attributes to be changed.

As this technically represents an ABI change it is not marked for
stable so any unlikely regressions are caught during a full release cycle.

Fixes: e9720acd728a ("[NET]: Make /proc/net a symlink on /proc/self/net (v3)")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/lkml/d0d111ef-edae-4760-83fb-36db84278da1@t-8ch.de/
Fixes: b4844fa0bdb4 ("selftests/nolibc: implement a few tests for various syscalls")
Tested-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Message-Id: <20230624-proc-net-setattr-v1-2-73176812adee@weissschuh.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Stable-dep-of: 6255da28d4bb ("proc: protect ptrace_may_access() with exec_update_lock (FD links)")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/proc/proc_net.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 707477e27f8317..b15b43d97dc9ed 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -310,6 +310,7 @@ static int proc_tgid_net_getattr(const struct path *path, struct kstat *stat,
 const struct inode_operations proc_net_inode_operations = {
 	.lookup		= proc_tgid_net_lookup,
 	.getattr	= proc_tgid_net_getattr,
+	.setattr        = proc_setattr,
 };
 
 static int proc_tgid_net_readdir(struct file *file, struct dir_context *ctx)
-- 
2.53.0