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23a0beaf3c
and associated inet_is_local_unbindable_port() helper function:
use it to make explicitly binding to an unbindable port return
-EPERM 'Operation not permitted'.
Autobind doesn't honour this new sysctl since:
(a) you can simply set both if that's the behaviour you desire
(b) there could be a use for preventing explicit while allowing auto
(c) it's faster in the relatively critical path of doing port selection
during connect() to only check one bitmap instead of both
Various ports may have special use cases which are not suitable for
use by general userspace applications. Currently, ports specified in
ip_local_reserved_ports sysctl will not be returned only in case of
automatic port assignment, but nothing prevents you from explicitly
binding to them - even from an entirely unprivileged process.
In certain cases it is desirable to prevent the host from assigning the
ports even in case of explicit binds, even from superuser processes.
Example use cases might be:
- a port being stolen by the nic for remote serial console, remote
power management or some other sort of debugging functionality
(crash collection, gdb, direct access to some other microcontroller
on the nic or motherboard, remote management of the nic itself).
- a transparent proxy where packets are being redirected: in case
a socket matches this connection, packets from this application
would be incorrectly sent to one of the endpoints.
Initially I wanted to solve this problem via the simple one line:
static inline bool inet_port_requires_bind_service(struct net *net, unsigned short port) {
- return port < net->ipv4.sysctl_ip_prot_sock;
+ return port < net->ipv4.sysctl_ip_prot_sock || inet_is_local_reserved_port(net, port);
}
However, this doesn't work for two reasons:
(a) it changes userspace visible behaviour of the existing local
reserved ports sysctl, and there appears to be enough documentation
on the internet talking about setting it to make this a bad idea
(b) it doesn't prevent privileged apps from using these ports,
CAP_BIND_SERVICE is relatively likely to be available to, for example,
a recursive DNS server so it can listed on port 53, which also needs
to do src port randomization for outgoing queries due to security
reasons (and it thus does manual port binding).
If we *know* that certain ports are simply unusable, then it's better
nothing even gets the opportunity to try to use them. This way we at
least get a quick failure, instead of some sort of timeout (or possibly
even corruption of the data stream of the non-kernel based use case).
Test:
vm:~# cat /proc/sys/net/ipv4/ip_local_unbindable_ports
vm:~# python -c 'import socket; s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0); s.bind(("::", 3967))'
vm:~# python -c 'import socket; s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, 0); s.bind(("::", 3967))'
vm:~# echo 3967 > /proc/sys/net/ipv4/ip_local_unbindable_ports
vm:~# cat /proc/sys/net/ipv4/ip_local_unbindable_ports
3967
vm:~# python -c 'import socket; s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, 0); s.bind(("::", 3967))'
socket.error: (1, 'Operation not permitted')
vm:~# python -c 'import socket; s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM, 0); s.bind(("::", 3967))'
socket.error: (1, 'Operation not permitted')
Cc: Sean Tranchetti <stranche@codeaurora.org>
Cc: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Linux SCTP <linux-sctp@vger.kernel.org>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Bug: 140404597
Change-Id: Ie96207bea90ae1345adf7b45724d0caf4d6e52c2
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
(cherry picked from commit 8a4b8ea595)
How do I submit patches to Android Common Kernels
-
BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.
- Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux,
additions of
EXPORT_SYMBOL_GPL()require an in-tree modular driver that uses the symbol -- so include the new driver or changes to an existing driver in the same patchset as the export. - When sending patches upstream, the commit message must contain a clear case for why the patch is needed and beneficial to the community. Enabling out-of-tree drivers or functionality is not not a persuasive case.
- Do not send patches upstream that contain only symbol exports. To be considered for upstream Linux,
additions of
-
LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.
Common Kernel patch requirements
- All patches must conform to the Linux kernel coding standards and pass
scripts/checkpatch.pl - Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
- If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch:
UPSTREAM:,BACKPORT:,FROMGIT:,FROMLIST:, orANDROID:. - All patches must have a
Change-Id:tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html) - If an Android bug has been assigned, there must be a
Bug:tag. - All patches must have a
Signed-off-by:tag by the author and the submitter
Additional requirements are listed below based on patch type
Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:
- If the patch is a cherry-pick from Linux mainline with no changes at all
- tag the patch subject with
UPSTREAM:. - add upstream commit information with a
(cherry picked from commit ...)line - Example:
- if the upstream commit message is
- tag the patch subject with
important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
UPSTREAM: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
(cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch requires any changes from the upstream version, tag the patch with
BACKPORT:instead ofUPSTREAM:.- use the same tags as
UPSTREAM: - add comments about the changes under the
(cherry picked from commit ...)line - Example:
- use the same tags as
BACKPORT: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
(cherry picked from commit c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
[joe: Resolved minor conflict in drivers/foo/bar.c ]
Signed-off-by: Joe Smith <joe.smith@foo.org>
Requirements for other backports: FROMGIT:, FROMLIST:,
- If the patch has been merged into an upstream maintainer tree, but has not yet
been merged into Linux mainline
- tag the patch subject with
FROMGIT: - add info on where the patch came from as
(cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't uselinux-nextfor example). - if changes were required, use
BACKPORT: FROMGIT: - Example:
- if the commit message in the maintainer tree is
- tag the patch subject with
important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
- then Joe Smith would upload the patch for the common kernel as
FROMGIT: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
(cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch has been submitted to LKML, but not accepted into any maintainer tree
- tag the patch subject with
FROMLIST: - add a
Link:tag with a link to the submittal on lore.kernel.org - add a
Bug:tag with the Android bug (required for patches not accepted into a maintainer tree) - if changes were required, use
BACKPORT: FROMLIST: - Example:
- tag the patch subject with
FROMLIST: important patch from upstream
This is the detailed description of the important patch
Signed-off-by: Fred Jones <fred.jones@foo.org>
Bug: 135791357
Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
Requirements for Android-specific patches: ANDROID:
- If the patch is fixing a bug to Android-specific code
- tag the patch subject with
ANDROID: - add a
Fixes:tag that cites the patch with the bug - Example:
- tag the patch subject with
ANDROID: fix android-specific bug in foobar.c
This is the detailed description of the important fix
Fixes: 1234abcd2468 ("foobar: add cool feature")
Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
Signed-off-by: Joe Smith <joe.smith@foo.org>
- If the patch is a new feature
- tag the patch subject with
ANDROID: - add a
Bug:tag with the Android bug (required for android-specific features)
- tag the patch subject with