From: Linus Torvalds torvalds@linux-foundation.org
stable inclusion from linux-4.19.195 commit 2bc534caba6a9650123e7ddb89b3e34845df9c7b
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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 leon@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Christian Brauner christian.brauner@ubuntu.com Cc: Andrea Righi andrea.righi@canonical.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- 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 e46c10acb784b..a8679c244e40a 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2537,7 +2537,9 @@ static int proc_pident_readdir(struct file *file, struct dir_context *ctx, #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,