Messages in this thread | | | Date | Wed, 26 Feb 2014 15:40:12 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE |
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Mathieu, you should have added a v2 to the subject ie: [PATCH V2]
Rusty,
If you want to take this, please add my Acked-by: Steven Rostedt <rostedt@goodmis.org>
-- 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);
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