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charset="UTF-8"; format="flowed" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: CAMSVWEXC01.scsc.local (2002:6a01:e347::6a01:e347) To CAMSVWEXC02.scsc.local (2002:6a01:e348::6a01:e348) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrGKsWRmVeSWpSXmKPExsWy7djP87r7ZCLSDabfNrG4M+k5u8W6t+dZ LS7vmsNm0TD7O6vFjQlPGS2WfnnHbLF0xVtWi82bpjI7cHh8vXmOyWPBplKPTas62TzenTvH 7rF+y1UWj8+b5ALYorhsUlJzMstSi/TtErgyZr9cwFhw06ei/+Rv5gbGJzZdjJwcEgImEuf/ PGbpYuTiEBJYwSgx49YyRgjnC6PE73MwzmdGiY9Ne9lgWn6/2sEMkVjOKHHz8wQ2uKpp35cy g1QJCexklLh/wQfE5hWwk7h/7xk7iM0ioCqxYeZdJoi4oMTJmU9YQGxRAXmJ+7dmgNUIC+RK tF17BhZnFhCXaPqykrWLkYNDREBF4tIjR5BdzALdTBI7Dy8Gq2cT0JTYd3ITmM0pYCOx5NkO dpB6ZgErieknPCHGyEs0b53NDPGAosSMiStZIOxaiVNbbjGBzJQQmMwp8WDvbXaIhIvEh6fb mSBsYYlXx7dAxWUkTk/ugWpOl1iybhaUXSCx5/YssDslBKwl+s7kQIQdJe5+3gwV5pO48VYQ 4hw+iUnbpjNPYFSdhRQQs5A8PAvhgVlIHljAyLKKUTy1tDg3PbXYMC+1XK84Mbe4NC9dLzk/ dxMjMCmd/nf80w7Gua8+6h1iZOJgPMQowcGsJMLL4R2aLsSbklhZlVqUH19UmpNafIhRmoNF SZxXNUU+VUggPbEkNTs1tSC1CCbLxMEp1cAks99g3U1Pw+Se7ilzVrO2ViwsZ894vGFn7P4N /nu8nntVWfzgX7js6OrF2XUzYqdEVFttMdbNUd4wc+oTY789pSUx88StOx+rXlh4P/Rx5Zqc NpaAN0kO7O8Xu3rlz3c8kup7O9Z1dmfYZKmY9A9+/itX3Zgb+KF69bqr9Yf3rLeU8xTV8Yso 3VogvnT3iYznJnYfNpkEBcv9sDk+Tyo0NHKrr3Cti+C9QtuXzv8jStPlG/m9n/ztdPdQClvu 9VdXTOfdz3W/jntu+MExaemMO7uXb9zWd2uL9S2zaUtkT9ZOUrHevD8k4PwEvn4HG3V3Ji8B Vs1fza4VceX50+cLrbKNTZD8UygmUby3P12JpTgj0VCLuag4EQDrGuKpuQMAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrLIsWRmVeSWpSXmKPExsVy+t/xu7r7ZCLSDa7sVbG4M+k5u8W6t+dZ LS7vmsNm0TD7O6vFjQlPGS2WfnnHbLF0xVtWi82bpjI7cHh8vXmOyWPBplKPTas62TzenTvH 7rF+y1UWj8+b5ALYovRsivJLS1IVMvKLS2yVog0tjPQMLS30jEws9QyNzWOtjEyV9O1sUlJz MstSi/TtEvQyZr9cwFhw06ei/+Rv5gbGJzZdjJwcEgImEr9f7WDuYuTiEBJYyiixsfMDO0RC RmLjl6usELawxJ9rXWwgtpDAR0aJd3OCIRp2Mkps//0JLMErYCdx/94zsGYWAVWJDTPvMkHE BSVOznzCAmKLCshL3L81A6xGWCBXou3aM7A4s4C4RNOXlUDLODhEBFQkLj1yBJnPLNDNJLHz 8GJ2iMUbWCT2veIHsdkENCX2ndwEFucUsJFY8mwHO8QcC4nFbw5C2fISzVtnM0M8oCgxY+JK Fgi7VuLz32eMExhFZyE5bxaSM2YhGTULyagFjCyrGEVSS4tz03OLjfSKE3OLS/PS9ZLzczcx AuN527GfW3Ywrnz1Ue8QIxMH4yFGCQ5mJRFeDu/QdCHelMTKqtSi/Pii0pzU4kOMpsAwmsgs JZqcD0woeSXxhmYGpoYmZpYGppZmxkrivGxXzqcJCaQnlqRmp6YWpBbB9DFxcEo1MIm1HJwb saP2Xo9F8T7L59P7zRKzFJ5fK7zo+sS+68bjaSoPBL5mnGKY9TRNSujrucdrokxYvNoOZ6+b lhfbtGv9uajUGv3rRu8uL15XMcNy/YPPyco2MfPn/AiZKBdh8mKfm0iNyEvtF3UB3iIzxSIP bV/vqmMn9EbHxaNN+/yVhQf3xmW2Gyj5T+m6wrPUvrxOMd7rveXevNyfV1+ccNp9L+RQVVRo 8bY/vO/YIqsTvnjILvrjWDq/gNnoZ+KMw9O+mF2Q2vymv7xz195JO6esfL/4clxBZNRMfn/m 4LenHc75Ky+71Hf3TyyT3/bNwTPOdWtnph/d8Z9hTRnP/wbTQzc277vML/g0qS7Jd4MSS3FG oqEWc1FxIgCrpqvPcAMAAA== X-CMS-MailID: 20241210104934eucas1p19459af12d0e83f45f9183eb1ab287757 X-Msg-Generator: CA X-RootMTR: 20241109103554eucas1p1548e0da57cccb9546a88402f1f5c94be X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20241109103554eucas1p1548e0da57cccb9546a88402f1f5c94be References: <737f952790c96a09ad5e51689918b97ef9b29174.1731148254.git.christophe.leroy@csgroup.eu> <164e5f22f8ab59d1d516e3c992efdd9f83ab4819.1731148254.git.christophe.leroy@csgroup.eu> <7fdcf601-524b-4530-861d-e4b0f8c1023b@suse.com> <9734d93d-73c8-464e-8f32-6117c6f6c952@samsung.com> On 12/4/2024 4:14 PM, Petr Pavlu wrote: > On 11/28/24 21:23, Daniel Gomez wrote: >> On 11/12/2024 3:35 PM, Petr Pavlu wrote: >>> On 11/12/24 10:43, Daniel Gomez wrote: >>>> On Mon Nov 11, 2024 at 7:53 PM CET, Christophe Leroy wrote: >>>>> >>>>> >>>>> Le 09/11/2024 à 23:17, Daniel Gomez a écrit : >>>>>> On Sat Nov 9, 2024 at 11:35 AM CET, Christophe Leroy wrote: >>>>>>> Once module init has succeded it is too late to cancel loading. >>>>>>> If setting ro_after_init data section to read-only fails, all we >>>>>>> can do is to inform the user through a warning. >>>>>>> >>>>>>> Reported-by: Thomas Gleixner >>>>>>> Closes: https://protect2.fireeye.com/v1/url?k=d3deb284-b2a35ac3-d3df39cb-74fe485fff30-288375d7d91e4ad9&q=1&e=701066ca-634d-4525-a77d-1a44451f897a&u=https%3A%2F%2Feur01.safelinks.protection.outlook.com%2F%3Furl%3Dhttps%253A%252F%252Flore.kernel.org%252Fall%252F20230915082126.4187913-1-ruanjinjie%2540huawei.com%252F%26data%3D05%257C02%257Cchristophe.leroy%2540csgroup.eu%257C26b5ca7363e54210439b08dd010c4865%257C8b87af7d86474dc78df45f69a2011bb5%257C0%257C0%257C638667874457200373%257CUnknown%257CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%253D%253D%257C0%257C%257C%257C%26sdata%3DZeJ%252F3%252B2Nx%252FBf%252FWLFEkhxKlDhZk8LNkz0fs%252Fg2xMcOjY%253D%26reserved%3D0 >>>>>>> Fixes: d1909c022173 ("module: Don't ignore errors from set_memory_XX()") >>>>>>> Signed-off-by: Christophe Leroy >>>>>>> --- >>>>>>> kernel/module/main.c | 6 +++--- >>>>>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>>>>> >>>>>>> diff --git a/kernel/module/main.c b/kernel/module/main.c >>>>>>> index 2de4ad7af335..1bf4b0db291b 100644 >>>>>>> --- a/kernel/module/main.c >>>>>>> +++ b/kernel/module/main.c >>>>>>> @@ -2583,7 +2583,9 @@ static noinline int do_init_module(struct module *mod) >>>>>>> #endif >>>>>>> ret = module_enable_rodata_ro_after_init(mod); >>>>>>> if (ret) >>>>>>> - goto fail_mutex_unlock; >>>>>>> + pr_warn("%s: %s() returned %d, ro_after_init data might still be writable\n", >>>>>>> + mod->name, __func__, ret); >>>>>>> + >>>>>>> mod_tree_remove_init(mod); >>>>>>> module_arch_freeing_init(mod); >>>>>>> for_class_mod_mem_type(type, init) { >>>>>>> @@ -2622,8 +2624,6 @@ static noinline int do_init_module(struct module *mod) >>>>>>> >>>>>>> return 0; >>>>>> >>>>>> I think it would make sense to propagate the error. But that would >>>>>> require changing modprobe.c. What kind of error can we expect when this >>>>>> happens? >>>>> >>>>> AFAIK, on powerpc it fails with EINVAL when >>>>> - The area is a vmalloc or module area and is a hugepage area >>>>> - The area is not vmalloc or io register and MMU is not powerpc radix MMU >>>>> >>>>> Otherwise it propagates the error from apply_to_existing_page_range(). >>>>> IIUC it will return EINVAL when it hits a leaf PTE in upper directories. >>>> >>>> Looking at that path I see we can also fail at __apply_to_page_range() >>>> -> apply_to_p4d_range() and return with -ENOMEM. >>>> >>>> My proposal was to do something like the change below in modprobe: >>>> >>>> diff --git a/tools/modprobe.c b/tools/modprobe.c >>>> index ec66e6f..8876e27 100644 >>>> --- a/tools/modprobe.c >>>> +++ b/tools/modprobe.c >>>> @@ -572,6 +572,11 @@ static int insmod_insert(struct kmod_module *mod, int flags, const char *extra_o >>>> err = 0; >>>> else { >>>> switch (err) { >>>> + case -EINVAL: >>>> + ERR("module '%s'inserted: ro_after_init data might" >>>> + "still be writable (see dmesg)\n", >>>> + kmod_module_get_name(mod)); >>>> + break; >>>> case -EEXIST: >>>> ERR("could not insert '%s': Module already in kernel\n", >>>> kmod_module_get_name(mod)); >>>> >>>> But I think these error codes may be also be reported in other parts >>>> such as simplify_symbols() so may not be a good idea after all. >>> >>> It isn't really possible to make a sensible use of the return code from >>> init_module(), besides some basic check for -EEXIST. The problem is that >>> any error code from a module's init function is also propagated as >>> a result from the syscall. >>> >>>> >>>> Maybe we just need to change the default/catch all error message in >>>> modprobe.c and to indicate/include this case: >>>> >>>> diff --git a/tools/modprobe.c b/tools/modprobe.c >>>> index ec66e6f..3647d37 100644 >>>> --- a/tools/modprobe.c >>>> +++ b/tools/modprobe.c >>>> @@ -582,7 +582,8 @@ static int insmod_insert(struct kmod_module *mod, int flags, const char *extra_o >>>> kmod_module_get_name(mod)); >>>> break; >>>> default: >>>> - ERR("could not insert '%s': %s\n", kmod_module_get_name(mod), >>>> + ERR("could not insert '%s' or inserted with error %s, " >>>> + "(see dmesg)\n", kmod_module_get_name(mod), >>>> strerror(-err)); >>>> break; >>>> } >>>> >>>> >>>>> >>>>> On other architectures it can be different, I know some architecture try >>>>> to split the pages when they hit hugepages and that can fail. >>>> >>>> Is it worth it adding an error code for this case in case we want to >>>> report it back? >>> >>> I feel that the proposed kernel warning about this situation is >>> sufficient and the loader should then return 0 to indicate that the >>> module got loaded. It would be more confusing to return an error but >>> with the module actually remaining inserted. >>> >>> A module loaded without having its RO-after-init section changed >>> properly to RO is still fully functional. In practice, if this final >>> set_memory_ro() call fails, the system is already in such a state where >>> the additional warning is the least of the issues? >>> >> >> __ro_after_init is used for kernel self protection. We are loading >> "successfully" the module yes, but variables with this attribute are >> marked read-only to reduce the attack surface [1]. Since we have >> considered this stage already too late to unload the module, IMHO we >> should at least indicate that there was an error during the module >> initialization and propagate that to the loader, so it can decide the >> best action for their particular case. Warning once in the kernel log >> system, does not seem sufficient to me. >> >> [1] Documentation/security/self-protection.rst > > I'd be careful about introducing this new state where (f)init_module() > returns an error, yet the module actually gets loaded. Perhaps we just need this new stage? module loaded with permission/security error? > > The init_module() interface has one return value which can originate > from anywhere during the load process, including from the module's own > init function. As mentioned, this means that the userspace cannot > distinguish why the module load failed. It would be needed to have > a specific error code returned only for this case, or to extend the > interface further in some way. > > Another concern is consistency of the module loader interface as > a whole. Returning an error from init_module() in this case would mean > that only the specific caller is made aware that the module was loaded > with some issues. A different task that then decides to check the module > state under /sys/module would see it as normally loaded, and similarly a Maybe we need to change this state too to indicate the problem. > task trying to insert it again would get -EEXIST. That likely would need > changing too. > > What I'd like to understand is how reporting this as an error to the > userspace would help in practice. I think the userspace can decide to > report it as a warning and continue, or treat is as a hard problem and > stop the system? I would expect that most tools/systems would opt for > the former, but then this doesn't seem much different to me than when > the kernel produces the warning itself. The second option, with some > stretch, could be implemented with panic_on_warn=1. Ideally, we would reverse the module initialization when encountering this error [1]. However, since it's not feasible to undo it correctly at this stage, reporting the error back to the caller allows them to assess and decide whether to accept the risk. [1] https://lore.kernel.org/all/Zuv0nmFblHUwuT8v@bombadil.infradead.org/ > > Do you envision that the userspace would handle this problem differently > and it is worth adding the complexity? What complexity do you mean? A module driver has ro_after_init for the purpose of protecting the kernel from attack [2]. If we ignore it by warning once, the caller will not be aware of such risk (unless the caller it's parsing the kernel log). [2] https://lore.kernel.org/all/1455748879-21872-1-git-send-email-keescook@chromium.org/ Another option could be adding a kconfig to decide to report or not which I would strongly suggest to report by default. > > As a side node, I've noticed that the module loader could mark also > static_call sections as ro_after_init. I'll post patches for that. > Additionally, both __jump_table and static_call sections could be > possibly turned RO earlier, after prepare_coming_module() -> > blocking_notifier_call_chain_robust() -> ... -> > jump_label_add_module()/static_call_add_module(). >