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1.. _stable_kernel_rules:2 3Everything you ever wanted to know about Linux -stable releases4===============================================================5 6Rules on what kind of patches are accepted, and which ones are not, into the7"-stable" tree:8 9- It or an equivalent fix must already exist in Linux mainline (upstream).10- It must be obviously correct and tested.11- It cannot be bigger than 100 lines, with context.12- It must follow the13 :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`14 rules.15- It must either fix a real bug that bothers people or just add a device ID.16 To elaborate on the former:17 18 - It fixes a problem like an oops, a hang, data corruption, a real security19 issue, a hardware quirk, a build error (but not for things marked20 CONFIG_BROKEN), or some "oh, that's not good" issue.21 - Serious issues as reported by a user of a distribution kernel may also22 be considered if they fix a notable performance or interactivity issue.23 As these fixes are not as obvious and have a higher risk of a subtle24 regression they should only be submitted by a distribution kernel25 maintainer and include an addendum linking to a bugzilla entry if it26 exists and additional information on the user-visible impact.27 - No "This could be a problem..." type of things like a "theoretical race28 condition", unless an explanation of how the bug can be exploited is also29 provided.30 - No "trivial" fixes without benefit for users (spelling changes, whitespace31 cleanups, etc).32 33 34Procedure for submitting patches to the -stable tree35----------------------------------------------------36 37.. note::38 39 Security patches should not be handled (solely) by the -stable review40 process but should follow the procedures in41 :ref:`Documentation/process/security-bugs.rst <securitybugs>`.42 43There are three options to submit a change to -stable trees:44 451. Add a 'stable tag' to the description of a patch you then submit for46 mainline inclusion.472. Ask the stable team to pick up a patch already mainlined.483. Submit a patch to the stable team that is equivalent to a change already49 mainlined.50 51The sections below describe each of the options in more detail.52 53:ref:`option_1` is **strongly** preferred, it is the easiest and most common.54:ref:`option_2` is mainly meant for changes where backporting was not considered55at the time of submission. :ref:`option_3` is an alternative to the two earlier56options for cases where a mainlined patch needs adjustments to apply in older57series (for example due to API changes).58 59When using option 2 or 3 you can ask for your change to be included in specific60stable series. When doing so, ensure the fix or an equivalent is applicable,61submitted, or already present in all newer stable trees still supported. This is62meant to prevent regressions that users might later encounter on updating, if63e.g. a fix merged for 5.19-rc1 would be backported to 5.10.y, but not to 5.15.y.64 65.. _option_1:66 67Option 168********69 70To have a patch you submit for mainline inclusion later automatically picked up71for stable trees, add this tag in the sign-off area::72 73 Cc: stable@vger.kernel.org74 75Use ``Cc: stable@kernel.org`` instead when fixing unpublished vulnerabilities:76it reduces the chance of accidentally exposing the fix to the public by way of77'git send-email', as mails sent to that address are not delivered anywhere.78 79Once the patch is mainlined it will be applied to the stable tree without80anything else needing to be done by the author or subsystem maintainer.81 82To send additional instructions to the stable team, use a shell-style inline83comment to pass arbitrary or predefined notes:84 85* Specify any additional patch prerequisites for cherry picking::86 87 Cc: <stable@vger.kernel.org> # 3.3.x: a1f84a3: sched: Check for idle88 Cc: <stable@vger.kernel.org> # 3.3.x: 1b9508f: sched: Rate-limit newidle89 Cc: <stable@vger.kernel.org> # 3.3.x: fd21073: sched: Fix affinity logic90 Cc: <stable@vger.kernel.org> # 3.3.x91 Signed-off-by: Ingo Molnar <mingo@elte.hu>92 93 The tag sequence has the meaning of::94 95 git cherry-pick a1f84a396 git cherry-pick 1b9508f97 git cherry-pick fd2107398 git cherry-pick <this commit>99 100 Note that for a patch series, you do not have to list as prerequisites the101 patches present in the series itself. For example, if you have the following102 patch series::103 104 patch1105 patch2106 107 where patch2 depends on patch1, you do not have to list patch1 as108 prerequisite of patch2 if you have already marked patch1 for stable109 inclusion.110 111* Point out kernel version prerequisites::112 113 Cc: <stable@vger.kernel.org> # 3.3.x114 115 The tag has the meaning of::116 117 git cherry-pick <this commit>118 119 For each "-stable" tree starting with the specified version.120 121 Note, such tagging is unnecessary if the stable team can derive the122 appropriate versions from Fixes: tags.123 124* Delay pick up of patches::125 126 Cc: <stable@vger.kernel.org> # after -rc3127 128* Point out known problems::129 130 Cc: <stable@vger.kernel.org> # see patch description, needs adjustments for <= 6.3131 132There furthermore is a variant of the stable tag you can use to make the stable133team's backporting tools (e.g AUTOSEL or scripts that look for commits134containing a 'Fixes:' tag) ignore a change::135 136 Cc: <stable+noautosel@kernel.org> # reason goes here, and must be present137 138.. _option_2:139 140Option 2141********142 143If the patch already has been merged to mainline, send an email to144stable@vger.kernel.org containing the subject of the patch, the commit ID,145why you think it should be applied, and what kernel versions you wish it to146be applied to.147 148.. _option_3:149 150Option 3151********152 153Send the patch, after verifying that it follows the above rules, to154stable@vger.kernel.org and mention the kernel versions you wish it to be applied155to. When doing so, you must note the upstream commit ID in the changelog of your156submission with a separate line above the commit text, like this::157 158 commit <sha1> upstream.159 160Or alternatively::161 162 [ Upstream commit <sha1> ]163 164If the submitted patch deviates from the original upstream patch (for example165because it had to be adjusted for the older API), this must be very clearly166documented and justified in the patch description.167 168 169Following the submission170------------------------171 172The sender will receive an ACK when the patch has been accepted into the173queue, or a NAK if the patch is rejected. This response might take a few174days, according to the schedules of the stable team members.175 176If accepted, the patch will be added to the -stable queue, for review by other177developers and by the relevant subsystem maintainer.178 179 180Review cycle181------------182 183- When the -stable maintainers decide for a review cycle, the patches will be184 sent to the review committee, and the maintainer of the affected area of185 the patch (unless the submitter is the maintainer of the area) and CC: to186 the linux-kernel mailing list.187- The review committee has 48 hours in which to ACK or NAK the patch.188- If the patch is rejected by a member of the committee, or linux-kernel189 members object to the patch, bringing up issues that the maintainers and190 members did not realize, the patch will be dropped from the queue.191- The ACKed patches will be posted again as part of release candidate (-rc)192 to be tested by developers and testers.193- Usually only one -rc release is made, however if there are any outstanding194 issues, some patches may be modified or dropped or additional patches may195 be queued. Additional -rc releases are then released and tested until no196 issues are found.197- Responding to the -rc releases can be done on the mailing list by sending198 a "Tested-by:" email with any testing information desired. The "Tested-by:"199 tags will be collected and added to the release commit.200- At the end of the review cycle, the new -stable release will be released201 containing all the queued and tested patches.202- Security patches will be accepted into the -stable tree directly from the203 security kernel team, and not go through the normal review cycle.204 Contact the kernel security team for more details on this procedure.205 206 207Trees208-----209 210- The queues of patches, for both completed versions and in progress211 versions can be found at:212 213 https://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git214 215- The finalized and tagged releases of all stable kernels can be found216 in separate branches per version at:217 218 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git219 220- The release candidate of all stable kernel versions can be found at:221 222 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/223 224 .. warning::225 The -stable-rc tree is a snapshot in time of the stable-queue tree and226 will change frequently, hence will be rebased often. It should only be227 used for testing purposes (e.g. to be consumed by CI systems).228 229 230Review committee231----------------232 233- This is made up of a number of kernel developers who have volunteered for234 this task, and a few that haven't.235