Bug 234722
| Summary: | [patch] [linux] getsockopt(SOL_SOCKET, SO_PEERCRED) on a Unix socket fails silently | ||||||||
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| Product: | Base System | Reporter: | Dániel Bakai <bakaidl> | ||||||
| Component: | kern | Assignee: | Mark Johnston <markj> | ||||||
| Status: | Closed FIXED | ||||||||
| Severity: | Affects Some People | CC: | bakaidl, markj | ||||||
| Priority: | --- | Keywords: | patch | ||||||
| Version: | 12.0-RELEASE | ||||||||
| Hardware: | Any | ||||||||
| OS: | Any | ||||||||
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The analysis seems right to me. I think the patch should add a comment explaining why we ignore the BSD level - do you mind adding one? SO_PASSCRED would need similar handling if it were ever implemented, so a comment would be a nice hint. Created attachment 200896 [details]
Patch with added comments
(In reply to Mark Johnston from comment #1) Thank you for the quick response. You're right, it's better to comment this, I've added a new patch (compat_linux_so_peercred_fix_v2.patch) containing one, I hope it's correct. A commit references this bug: Author: markj Date: Tue Jan 8 17:21:59 UTC 2019 New revision: 342864 URL: https://svnweb.freebsd.org/changeset/base/342864 Log: Specify the correct option level when emulating SO_PEERCRED. Our equivalent to SO_PEERCRED, LOCAL_PEERCRED, is implemented at socket option level 0, not SOL_SOCKET. PR: 234722 Submitted by: D?niel Bakai <bakaidl@gmail.com> MFC after: 2 weeks Changes: head/sys/compat/linux/linux_socket.c (In reply to Dániel Bakai from comment #3) Thank you. I committed a minor variation of your patch to head. A commit references this bug: Author: markj Date: Tue Jan 22 02:02:13 UTC 2019 New revision: 343293 URL: https://svnweb.freebsd.org/changeset/base/343293 Log: MFC r342864: Specify the correct option level when emulating SO_PEERCRED. PR: 234722 Changes: _U stable/12/ stable/12/sys/compat/linux/linux_socket.c A commit references this bug: Author: markj Date: Tue Jan 22 02:04:37 UTC 2019 New revision: 343294 URL: https://svnweb.freebsd.org/changeset/base/343294 Log: MFC r342864: Specify the correct option level when emulating SO_PEERCRED. PR: 234722 Changes: _U stable/11/ stable/11/sys/compat/linux/linux_socket.c Thank you for the patch. (In reply to Mark Johnston from comment #8) Thank you for merging it so fast. |
Created attachment 200893 [details] Source for reproduction and patch When using the SO_PEERCRED getsockopt for a Unix socket from a Linux program with the Linux compatibility layer, it returns with no error, but the resulting struct ucred contains garbage. To reproduce, compile the attached linux_peercred_test.c for Linux, set up a listening Unix socket named test.sock on FreeBSD (nc -l -U test.sock or socat UNIX-LISTEN:test.sock -) and run linux_peercred_test. It will return something along the line of this: [bakaid@freebsd ~]$ ./linux_peercred_test uid: 4294965248, gid: 6, pid: 0 The cause seem to be the following: The Linux compat layer translates the Linux getsockopt for level SOL_SOCKET (1), optname SO_PEERCRED (17) to level SOL_SOCKET (0xffff), optname LOCAL_PEERCRED (1), and calls kern_getsockopt (sys/kern/uipc_syscalls.c) with these parameters (sys/compat/linux/linux_socket.c). However, LOCAL_PEERCRED should be called with level 0, not level SOL_SOCKET, as demonstrated (among others) by the getpeereid implementation (lib/libc/gen/getpeereid.c). Even worse, calling it with SOL_SOCKET will cause the getsockopt being served as a SOL_SOCKET request (kern_getsockopt -> sogetopt (sys/kern/uipc_socket.c)) and interpreted as SO_DEBUG (1), which will return successfully, causing the failure to be silent. I've only tried this on FreeBSD 12.0-RELEASE r341666 GENERIC amd64, but looking through the relevant git history I don't see positive evidence that this function ever worked properly. The attached patch (compat_linux_so_peercred_fix.patch) fixes the issue, which can be verified by running linux_peercred_test again: [bakaid@freebsd ~]$ ./linux_peercred_test uid: 1001, gid: 1001, pid: 0