From 94f0b2d4a1d0c52035aef425da5e022bd2cb1c71 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 15 Jun 2021 09:26:19 -0700 Subject: [PATCH] proc: only require mm_struct for writing Commit 591a22c14d3f ("proc: Track /proc/$pid/attr/ opener mm_struct") we started using __mem_open() to track the mm_struct at open-time, so that we could then check it for writes. But that also ended up making the permission checks at open time much stricter - and not just for writes, but for reads too. And that in turn caused a regression for at least Fedora 29, where NIC interfaces fail to start when using NetworkManager. Since only the write side wanted the mm_struct test, ignore any failures by __mem_open() at open time, leaving reads unaffected. The write() time verification of the mm_struct pointer will then catch the failure case because a NULL pointer will not match a valid 'current->mm'. Link: https://lore.kernel.org/netdev/YMjTlp2FSJYvoyFa@unreal/ Fixes: 591a22c14d3f ("proc: Track /proc/$pid/attr/ opener mm_struct") Reported-and-tested-by: Leon Romanovsky Cc: Kees Cook Cc: Christian Brauner Cc: Andrea Righi Signed-off-by: Linus Torvalds --- fs/proc/base.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 7118ebe38fa6..9cbd915025ad 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2676,7 +2676,9 @@ out: #ifdef CONFIG_SECURITY static int proc_pid_attr_open(struct inode *inode, struct file *file) { - return __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS); + file->private_data = NULL; + __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS); + return 0; } static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,