lkml.org 
[lkml]   [2021]   [Jul]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] seccomp_unotify.2: Add doc for SECCOMP_ADDFD_FLAG_SEND
Date
This flag was recently added to Linux 5.14 by a patch I wrote:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0ae71c7720e3ae3aabd2e8a072d27f7bd173d25c

This patch adds documentation for the flag, the error code that the flag
added and explains in the caveat when it is useful.

Signed-off-by: Rodrigo Campos <rodrigo@kinvolk.io>
---
Hi! Here goes the documentation for the flag I just added. Please feel free to
amend as you want and let me know if something is not clear :)


man2/seccomp_unotify.2 | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/man2/seccomp_unotify.2 b/man2/seccomp_unotify.2
index 2673d9bc7..9bd27214f 100644
--- a/man2/seccomp_unotify.2
+++ b/man2/seccomp_unotify.2
@@ -739,6 +739,17 @@ When allocating the file descriptor in the target,
use the file descriptor number specified in the
.I newfd
field.
+.TP
+.BR SECCOMP_ADDFD_FLAG_SEND
+Available since Linux 5.14, combines the
+.B SECCOMP_IOCTL_NOTIF_ADDFD
+ioctl with
+.B SECCOMP_IOCTL_NOTIF_SEND
+into an atomic operation. On successful invocation, the target process's
+errno will be 0 and the return value will be the file descriptor number that was
+installed in the target. If allocating the file descriptor in the tatget fails,
+the target's syscall continues to be blocked until a successful response is
+sent.
.RE
.TP
.I srcfd
@@ -801,6 +812,13 @@ Allocating the file descriptor in the target would cause the target's
limit to be exceeded (see
.BR getrlimit (2)).
.TP
+.B EBUSY
+If the flag
+.B SECCOMP_IOCTL_NOTIF_SEND
+is used, this means the operation can't proceed until other
+.B SECCOMP_IOCTL_NOTIF_ADDFD
+requests are processed.
+.TP
.B EINPROGRESS
The user-space notification specified in the
.I id
@@ -1131,6 +1149,14 @@ that would
normally be restarted by the
.BR SA_RESTART
flag.
+.PP
+Furthermore, if the supervisor response is a file descriptor
+added with
+.B SECCOMP_IOCTL_NOTIF_ADDFD,
+then the flag
+.B SECCOMP_ADDFD_FLAG_SEND
+can be used to atomically add the file descriptor and return that value,
+making sure no file descriptors are inadvertently leaked into the target.
.\" FIXME
.\" About the above, Kees Cook commented:
.\"
--
2.30.2
\
 
 \ /
  Last update: 2021-07-02 18:38    [W:0.061 / U:0.516 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site