Messages in this thread Patch in this message | | | Date | Wed, 26 Feb 2014 21:24:52 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH] Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE |
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----- Original Message ----- > From: "Steven Rostedt" <rostedt@goodmis.org> > To: "Mathieu Desnoyers" <mathieu.desnoyers@efficios.com> > Cc: linux-kernel@vger.kernel.org, "Ingo Molnar" <mingo@redhat.com>, "Thomas Gleixner" <tglx@linutronix.de>, "Rusty > Russell" <rusty@rustcorp.com.au>, "David Howells" <dhowells@redhat.com>, "Greg Kroah-Hartman" > <gregkh@linuxfoundation.org> > Sent: Wednesday, February 26, 2014 3:40:12 PM > Subject: Re: [PATCH] Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE > > Mathieu, you should have added a v2 to the subject ie: [PATCH V2]
Good point, I'll keep in mind to increment patch version between RFC PATCH and PATCH when there are changes. Indeed, it can be confusing otherwise.
> > Rusty, > > If you want to take this, please add my > Acked-by: Steven Rostedt <rostedt@goodmis.org>
Thanks!
Mathieu
> > -- Steve > > > On Fri, 14 Feb 2014 00:18:26 -0500 > Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote: > > > Users have reported being unable to trace non-signed modules loaded > > within a kernel supporting module signature. > > > > This is caused by tracepoint.c:tracepoint_module_coming() refusing to > > take into account tracepoints sitting within force-loaded modules > > (TAINT_FORCED_MODULE). The reason for this check, in the first place, is > > that a force-loaded module may have a struct module incompatible with > > the layout expected by the kernel, and can thus cause a kernel crash > > upon forced load of that module on a kernel with CONFIG_TRACEPOINTS=y. > > > > Tracepoints, however, specifically accept TAINT_OOT_MODULE and > > TAINT_CRAP, since those modules do not lead to the "very likely system > > crash" issue cited above for force-loaded modules. > > > > With kernels having CONFIG_MODULE_SIG=y (signed modules), a non-signed > > module is tainted re-using the TAINT_FORCED_MODULE taint flag. > > Unfortunately, this means that Tracepoints treat that module as a > > force-loaded module, and thus silently refuse to consider any tracepoint > > within this module. > > > > Since an unsigned module does not fit within the "very likely system > > crash" category of tainting, add a new TAINT_UNSIGNED_MODULE taint flag > > to specifically address this taint behavior, and accept those modules > > within Tracepoints. We use the letter 'X' as a taint flag character for > > a module being loaded that doesn't know how to sign its name (proposed > > by Steven Rostedt). > > > > Also add the missing 'O' entry to trace event show_module_flags() list > > for the sake of completeness. > > > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > > CC: Steven Rostedt <rostedt@goodmis.org> > > CC: Ingo Molnar <mingo@redhat.com> > > CC: Thomas Gleixner <tglx@linutronix.de> > > CC: Rusty Russell <rusty@rustcorp.com.au> > > CC: David Howells <dhowells@redhat.com> > > CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > > --- > > Documentation/ABI/testing/sysfs-module | 1 + > > Documentation/module-signing.txt | 3 ++- > > Documentation/oops-tracing.txt | 3 +++ > > Documentation/sysctl/kernel.txt | 2 ++ > > include/linux/kernel.h | 1 + > > include/trace/events/module.h | 4 +++- > > kernel/module.c | 4 +++- > > kernel/panic.c | 2 ++ > > kernel/tracepoint.c | 5 +++-- > > 9 files changed, 20 insertions(+), 5 deletions(-) > > > > diff --git a/Documentation/ABI/testing/sysfs-module > > b/Documentation/ABI/testing/sysfs-module > > index 47064c2..b9a29cd 100644 > > --- a/Documentation/ABI/testing/sysfs-module > > +++ b/Documentation/ABI/testing/sysfs-module > > @@ -49,3 +49,4 @@ Description: Module taint flags: > > O - out-of-tree module > > F - force-loaded module > > C - staging driver module > > + X - unsigned module > > diff --git a/Documentation/module-signing.txt > > b/Documentation/module-signing.txt > > index 2b40e04..b6af42e 100644 > > --- a/Documentation/module-signing.txt > > +++ b/Documentation/module-signing.txt > > @@ -53,7 +53,8 @@ This has a number of options available: > > > > If this is off (ie. "permissive"), then modules for which the key is > > not > > available and modules that are unsigned are permitted, but the kernel > > will > > - be marked as being tainted. > > + be marked as being tainted, and the concerned modules will be marked > > as > > + tainted, shown with the character 'X'. > > > > If this is on (ie. "restrictive"), only modules that have a valid > > signature that can be verified by a public key in the kernel's > > possession > > diff --git a/Documentation/oops-tracing.txt > > b/Documentation/oops-tracing.txt > > index 13032c0..879abe2 100644 > > --- a/Documentation/oops-tracing.txt > > +++ b/Documentation/oops-tracing.txt > > @@ -265,6 +265,9 @@ characters, each representing a particular tainted > > value. > > > > 13: 'O' if an externally-built ("out-of-tree") module has been loaded. > > > > + 14: 'X' if an unsigned module has been loaded in a kernel supporting > > + module signature. > > + > > The primary reason for the 'Tainted: ' string is to tell kernel > > debuggers if this is a clean kernel or if anything unusual has > > occurred. Tainting is permanent: even if an offending module is > > diff --git a/Documentation/sysctl/kernel.txt > > b/Documentation/sysctl/kernel.txt > > index e55124e..8ebe1c0 100644 > > --- a/Documentation/sysctl/kernel.txt > > +++ b/Documentation/sysctl/kernel.txt > > @@ -792,6 +792,8 @@ can be ORed together: > > 1024 - A module from drivers/staging was loaded. > > 2048 - The system is working around a severe firmware bug. > > 4096 - An out-of-tree module has been loaded. > > +8192 - An unsigned module has been loaded in a kernel supporting module > > + signature. > > > > ============================================================== > > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > index 196d1ea..4710900 100644 > > --- a/include/linux/kernel.h > > +++ b/include/linux/kernel.h > > @@ -469,6 +469,7 @@ extern enum system_states { > > #define TAINT_CRAP 10 > > #define TAINT_FIRMWARE_WORKAROUND 11 > > #define TAINT_OOT_MODULE 12 > > +#define TAINT_UNSIGNED_MODULE 13 > > > > extern const char hex_asc[]; > > #define hex_asc_lo(x) hex_asc[((x) & 0x0f)] > > diff --git a/include/trace/events/module.h b/include/trace/events/module.h > > index 1619327..11fd51b 100644 > > --- a/include/trace/events/module.h > > +++ b/include/trace/events/module.h > > @@ -22,8 +22,10 @@ struct module; > > > > #define show_module_flags(flags) __print_flags(flags, "", \ > > { (1UL << TAINT_PROPRIETARY_MODULE), "P" }, \ > > + { (1UL << TAINT_OOT_MODULE), "O" }, \ > > { (1UL << TAINT_FORCED_MODULE), "F" }, \ > > - { (1UL << TAINT_CRAP), "C" }) > > + { (1UL << TAINT_CRAP), "C" }, \ > > + { (1UL << TAINT_UNSIGNED_MODULE), "X" }) > > > > TRACE_EVENT(module_load, > > > > diff --git a/kernel/module.c b/kernel/module.c > > index d24fcf2..4d7d25e 100644 > > --- a/kernel/module.c > > +++ b/kernel/module.c > > @@ -1013,6 +1013,8 @@ static size_t module_flags_taint(struct module *mod, > > char *buf) > > buf[l++] = 'F'; > > if (mod->taints & (1 << TAINT_CRAP)) > > buf[l++] = 'C'; > > + if (mod->taints & (1 << TAINT_UNSIGNED_MODULE)) > > + buf[l++] = 'X'; > > /* > > * TAINT_FORCED_RMMOD: could be added. > > * TAINT_UNSAFE_SMP, TAINT_MACHINE_CHECK, TAINT_BAD_PAGE don't > > @@ -3214,7 +3216,7 @@ static int load_module(struct load_info *info, const > > char __user *uargs, > > pr_notice_once("%s: module verification failed: signature " > > "and/or required key missing - tainting " > > "kernel\n", mod->name); > > - add_taint_module(mod, TAINT_FORCED_MODULE, LOCKDEP_STILL_OK); > > + add_taint_module(mod, TAINT_UNSIGNED_MODULE, LOCKDEP_STILL_OK); > > } > > #endif > > > > diff --git a/kernel/panic.c b/kernel/panic.c > > index 6d63003..0e25fe1 100644 > > --- a/kernel/panic.c > > +++ b/kernel/panic.c > > @@ -210,6 +210,7 @@ static const struct tnt tnts[] = { > > { TAINT_CRAP, 'C', ' ' }, > > { TAINT_FIRMWARE_WORKAROUND, 'I', ' ' }, > > { TAINT_OOT_MODULE, 'O', ' ' }, > > + { TAINT_UNSIGNED_MODULE, 'X', ' ' }, > > }; > > > > /** > > @@ -228,6 +229,7 @@ static const struct tnt tnts[] = { > > * 'C' - modules from drivers/staging are loaded. > > * 'I' - Working around severe firmware bug. > > * 'O' - Out-of-tree module has been loaded. > > + * 'X' - Unsigned module has been loaded. > > * > > * The string is overwritten by the next call to print_tainted(). > > */ > > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c > > index 29f2654..9bb887d 100644 > > --- a/kernel/tracepoint.c > > +++ b/kernel/tracepoint.c > > @@ -639,9 +639,10 @@ static int tracepoint_module_coming(struct module > > *mod) > > /* > > * We skip modules that taint the kernel, especially those with different > > * module headers (for forced load), to make sure we don't cause a crash. > > - * Staging and out-of-tree GPL modules are fine. > > + * Staging, out-of-tree, and unsigned GPL modules are fine. > > */ > > - if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP))) > > + if (mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) | > > + (1 << TAINT_UNSIGNED_MODULE))) > > return 0; > > mutex_lock(&tracepoints_mutex); > > tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL); > >
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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