On Tue, Nov 19, 2019 at 09:51:49AM -0600, Tianlin Li wrote: > Right now several architectures allow their set_memory_*() family of > functions to fail, but callers may not be checking the return values. We > need to fix the callers and add the __must_check attribute. Please formulate commit messages in passive tone. "we" is ambiguous. >From Documentation/process/submitting-patches.rst: "Describe your changes in imperative mood, e.g. "make xyzzy do frotz" instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy to do frotz", as if you are giving orders to the codebase to change its behaviour." Also, you could add a high-level summary of the failure case from: https://lore.kernel.org/netdev/20180628213459.28631-4-daniel@xxxxxxxxxxxxx/ as a more real-life, convincing justification for this. > They also may not provide any level of atomicity, in the sense that > the memory protections may be left incomplete on failure. > This issue likely has a few > steps on effects architectures[1]: > 1)Have all callers of set_memory_*() helpers check the return value. > 2)Add __much_check to all set_memory_*() helpers so that new uses do not __must_check > ignore the return value. > 3)Add atomicity to the calls so that the memory protections aren't left in > a partial state. > > Ideally, the failure of set_memory_*() should be passed up the call stack, > and callers should examine the failure and deal with it. But currently, > some callers just have void return type. > > We need to fix the callers to handle the return all the way to the top of > stack, and it will require a large series of patches to finish all the three > steps mentioned above. I start with kernel/module, and will move onto other > subsystems. I am not entirely sure about the failure modes for each caller. > So I would like to get some comments before I move forward. This single > patch is just for fixing the return value of set_memory_*() function in > kernel/module, and also the related callers. Any feedback would be greatly > appreciated. > > [1]:https://github.com/KSPP/linux/issues/7 > > Signed-off-by: Tianlin Li <tli@xxxxxxxxxxxxxxxx> > --- > arch/arm/kernel/ftrace.c | 8 +- > arch/arm64/kernel/ftrace.c | 6 +- > arch/nds32/kernel/ftrace.c | 6 +- > arch/x86/kernel/ftrace.c | 13 ++- > include/linux/module.h | 16 ++-- > kernel/livepatch/core.c | 15 +++- > kernel/module.c | 170 +++++++++++++++++++++++++++---------- > kernel/trace/ftrace.c | 15 +++- > 8 files changed, 175 insertions(+), 74 deletions(-) Yeah, general idea makes sense but you'd need to redo your patch ontop of linux-next because there are some changes in flight in ftrace-land at least and your patch won't apply anymore after next week, when the merge window opens. Also, you should use checkpatch before sending a patch as sometimes it makes sense what it complains about: WARNING: Missing a blank line after declarations #79: FILE: arch/arm/kernel/ftrace.c:68: + int ret; + ret = set_all_modules_text_ro(); WARNING: Missing a blank line after declarations #150: FILE: arch/x86/kernel/ftrace.c:61: + int ret; + ret = set_all_modules_text_ro(); WARNING: trailing semicolon indicates no statements, indent implies otherwise #203: FILE: kernel/livepatch/core.c:731: + if (module_enable_ro(patch->mod, true)); + pr_err("module_enable_ro failed.\n"); ERROR: trailing statements should be on next line #203: FILE: kernel/livepatch/core.c:731: + if (module_enable_ro(patch->mod, true)); WARNING: Missing a blank line after declarations #451: FILE: kernel/module.c:2091: + int ret; + ret = frob_text(&mod->core_layout, set_memory_x); WARNING: Missing a blank line after declarations #511: FILE: kernel/trace/ftrace.c:5819: + int ret = ftrace_arch_code_modify_prepare(); + if (ret) { WARNING: Missing a blank line after declarations #527: FILE: kernel/trace/ftrace.c:5864: + int ret = ftrace_arch_code_modify_post_process(); + FTRACE_WARN_ON(ret); > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > index c4ce08f43bd6..39bfc0685854 100644 > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -721,16 +721,25 @@ static int klp_init_object_loaded(struct klp_patch *patch, > > mutex_lock(&text_mutex); > > - module_disable_ro(patch->mod); > + ret = module_disable_ro(patch->mod); > + if (ret) { > + mutex_unlock(&text_mutex); > + return ret; > + } > ret = klp_write_object_relocations(patch->mod, obj); > if (ret) { > - module_enable_ro(patch->mod, true); > + if (module_enable_ro(patch->mod, true)); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ and if you look at its output above closely, it might even help you catch the bug you've added. [ Don't worry, happens to the best of us. :-) ] Also, what would help review is if you split your patch: patch 1: Change functions to return a retval patch 2-n: Change call sites to handle retval properly Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
