From: Linus Torvalds Date: Tue, 15 Jun 2021 16:26:19 +0000 (-0700) Subject: proc: only require mm_struct for writing X-Git-Tag: v5.10.79~3656 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=ef9a0d224bafc0f4f8f85d0eb69fc59a6fbd1318;p=platform%2Fkernel%2Flinux-rpi.git proc: only require mm_struct for writing commit 94f0b2d4a1d0c52035aef425da5e022bd2cb1c71 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/proc/base.c b/fs/proc/base.c index 511d98d..df9b17d 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2677,7 +2677,9 @@ 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,