Re: [PATCH v3 4/6] pstore/ram: Introduce max_reason and convert dump_oops

Kees Cook
2020-05-12T23:57:48Z

On Tue, May 12, 2020 at 06:35:04PM -0500, Tyler Hicks wrote:
> On 2020-05-06 14:15:21, Kees Cook wrote:
> > From: Pavel Tatashin <pasha.tatashin@soleen.com>
> >
> > Now that pstore_register() can correctly pass max_reason to the kmesg
> > dump facility, introduce a new "max_reason" module parameter and
> > "max-reason" Device Tree field.
> >
> > The "dump_oops" module parameter and "dump-oops" Device
> > Tree field are now considered deprecated, but are now automatically
> > converted to their corresponding max_reason values when present, though
> > the new max_reason setting has precedence.
> >
> > For struct ramoops_platform_data, the "dump_oops" member is entirely
> > replaced by a new "max_reason" member, with the only existing user
> > updated in place.
> >
> > Additionally remove the "reason" filter logic from ramoops_pstore_write(),
> > as that is not specifically needed anymore, though technically
> > this is a change in behavior for any ramoops users also setting the
> > printk.always_kmsg_dump boot param, which will cause ramoops to behave as
> > if max_reason was set to KMSG_DUMP_MAX.
> >
> > Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
> > Link: https://lore.kernel.org/r/20200505154510.93506-4-pasha.tatashin@soleen.com
> > Link: https://lore.kernel.org/r/20200505154510.93506-5-pasha.tatashin@soleen.com
> > Co-developed-by: Kees Cook <keescook@chromium.org>
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > Documentation/admin-guide/ramoops.rst | 14 +++++--
> > drivers/platform/chrome/chromeos_pstore.c | 2 +-
> > fs/pstore/ram.c | 51 +++++++++++++++--------
> > include/linux/pstore_ram.h | 2 +-
> > 4 files changed, 45 insertions(+), 24 deletions(-)
> >
> > diff --git a/Documentation/admin-guide/ramoops.rst b/Documentation/admin-guide/ramoops.rst
> > index 6dbcc5481000..a60a96218ba9 100644
> > --- a/Documentation/admin-guide/ramoops.rst
> > +++ b/Documentation/admin-guide/ramoops.rst
> > @@ -32,11 +32,17 @@ memory to be mapped strongly ordered, and atomic operations on strongly ordered
> > memory are implementation defined, and won't work on many ARMs such as omaps.
> >
> > The memory area is divided into ``record_size`` chunks (also rounded down to
> > -power of two) and each oops/panic writes a ``record_size`` chunk of
> > +power of two) and each kmesg dump writes a ``record_size`` chunk of
> > information.
> >
> > -Dumping both oopses and panics can be done by setting 1 in the ``dump_oops``
> > -variable while setting 0 in that variable dumps only the panics.
> > +Limiting which kinds of kmsg dumps are stored can be controlled via
> > +the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's
> > +``enum kmsg_dump_reason``. For example, to store both Oopses and Panics,
> > +``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics
> > +``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0
> > +(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the
> > +``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS,
> > +otherwise KMSG_DUMP_MAX.
> >
> > The module uses a counter to record multiple dumps but the counter gets reset
> > on restart (i.e. new dumps after the restart will overwrite old ones).
> > @@ -90,7 +96,7 @@ Setting the ramoops parameters can be done in several different manners:
> > .mem_address = <...>,
> > .mem_type = <...>,
> > .record_size = <...>,
> > - .dump_oops = <...>,
> > + .max_reason = <...>,
> > .ecc = <...>,
> > };
> >
> > diff --git a/drivers/platform/chrome/chromeos_pstore.c b/drivers/platform/chrome/chromeos_pstore.c
> > index d13770785fb5..fa51153688b4 100644
> > --- a/drivers/platform/chrome/chromeos_pstore.c
> > +++ b/drivers/platform/chrome/chromeos_pstore.c
> > @@ -57,7 +57,7 @@ static struct ramoops_platform_data chromeos_ramoops_data = {
> > .record_size = 0x40000,
> > .console_size = 0x20000,
> > .ftrace_size = 0x20000,
> > - .dump_oops = 1,
> > + .max_reason = KMSG_DUMP_OOPS,
> > };
> >
> > static struct platform_device chromeos_ramoops = {
> > diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> > index c2f76b650f91..b8dac1d04e96 100644
> > --- a/fs/pstore/ram.c
> > +++ b/fs/pstore/ram.c
> > @@ -57,10 +57,15 @@ module_param(mem_type, uint, 0600);
> > MODULE_PARM_DESC(mem_type,
> > "set to 1 to try to use unbuffered memory (default 0)");
> >
> > -static int dump_oops = 1;
> > -module_param(dump_oops, int, 0600);
> > +static int ramoops_dump_oops = -1;
> > +module_param_named(dump_oops, ramoops_dump_oops, int, 0400);
> > MODULE_PARM_DESC(dump_oops,
> > - "set to 1 to dump oopses, 0 to only dump panics (default 1)");
> > + "set to 1 to dump oopses & panics, 0 to only dump panics (deprecated: use max_reason instead)");
> > +
> > +static int ramoops_max_reason = KMESG_DUMP_OOPS;
> > +module_param_named(max_reason, ramoops_max_reason, int, 0400);
> > +MODULE_PARM_DESC(max_reason,
> > + "maximum reason for kmsg dump (default 2: Oops and Panic) ");
> >
> > static int ramoops_ecc;
> > module_param_named(ecc, ramoops_ecc, int, 0600);
> > @@ -81,7 +86,6 @@ struct ramoops_context {
> > size_t console_size;
> > size_t ftrace_size;
> > size_t pmsg_size;
> > - int dump_oops;
> > u32 flags;
> > struct persistent_ram_ecc_info ecc_info;
> > unsigned int max_dump_cnt;
> > @@ -382,16 +386,14 @@ static int notrace ramoops_pstore_write(struct pstore_record *record)
> > return -EINVAL;
> >
> > /*
> > - * Out of the various dmesg dump types, ramoops is currently designed
> > - * to only store crash logs, rather than storing general kernel logs.
> > + * We could filter on record->reason here if we wanted to (which
> > + * would duplicate what happened before the "max_reason" setting
> > + * was added), but that would defeat the purpose of a system
> > + * changing printk.always_kmsg_dump, so instead log everything that
> > + * the kmsg dumper sends us, since it should be doing the filtering
> > + * based on the combination of printk.always_kmsg_dump and our
> > + * requested "max_reason".
> > */
> > - if (record->reason != KMSG_DUMP_OOPS &&
> > - record->reason != KMSG_DUMP_PANIC)
> > - return -EINVAL;
> > -
> > - /* Skip Oopes when configured to do so. */
> > - if (record->reason == KMSG_DUMP_OOPS && !cxt->dump_oops)
> > - return -EINVAL;
> >
> > /*
> > * Explicitly only take the first part of any new crash.
> > @@ -692,7 +694,14 @@ static int ramoops_parse_dt(struct platform_device *pdev,
> > pdata->mem_size = resource_size(res);
> > pdata->mem_address = res->start;
> > pdata->mem_type = of_property_read_bool(of_node, "unbuffered");
> > - pdata->dump_oops = !of_property_read_bool(of_node, "no-dump-oops");
> > + /*
> > + * Setting "no-dump-oops" is deprecated and will be ignored if
> > + * "max_reason" is also specified.
> > + */
> > + if (of_property_read_bool(of_node, "no-dump-oops"))
> > + pdata->max_reason = KMSG_DUMP_PANIC;
> > + else
> > + pdata->max_reason = KMSG_DUMP_OOPS;
> >
> > #define parse_size(name, field, default_value) { \
> > ret = ramoops_parse_dt_size(pdev, name, default_value, \
> > @@ -708,6 +717,7 @@ static int ramoops_parse_dt(struct platform_device *pdev,
> > parse_size("pmsg-size", pdata->pmsg_size, 0);
> > parse_size("ecc-size", pdata->ecc_info.ecc_size, 0);
> > parse_size("flags", pdata->flags, 0);
> > + parse_size("max-reason", pdata->max_reason, pdata->max_reason);
> >
> > #undef parse_size
> >
> > @@ -791,7 +801,6 @@ static int ramoops_probe(struct platform_device *pdev)
> > cxt->console_size = pdata->console_size;
> > cxt->ftrace_size = pdata->ftrace_size;
> > cxt->pmsg_size = pdata->pmsg_size;
> > - cxt->dump_oops = pdata->dump_oops;
> > cxt->flags = pdata->flags;
> > cxt->ecc_info = pdata->ecc_info;
> >
> > @@ -834,8 +843,10 @@ static int ramoops_probe(struct platform_device *pdev)
> > * the single region size is how to check.
> > */
> > cxt->pstore.flags = 0;
> > - if (cxt->max_dump_cnt)
> > + if (cxt->max_dump_cnt) {
> > cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
> > + cxt->pstore.max_reason = pdata->max_reason;
> > + }
> > if (cxt->console_size)
> > cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
> > if (cxt->max_ftrace_cnt)
> > @@ -871,7 +882,7 @@ static int ramoops_probe(struct platform_device *pdev)
> > mem_size = pdata->mem_size;
> > mem_address = pdata->mem_address;
> > record_size = pdata->record_size;
> > - dump_oops = pdata->dump_oops;
> > + ramoops_max_reason = pdata->max_reason;
> > ramoops_console_size = pdata->console_size;
> > ramoops_pmsg_size = pdata->pmsg_size;
> > ramoops_ftrace_size = pdata->ftrace_size;
> > @@ -954,7 +965,11 @@ static void __init ramoops_register_dummy(void)
> > pdata.console_size = ramoops_console_size;
> > pdata.ftrace_size = ramoops_ftrace_size;
> > pdata.pmsg_size = ramoops_pmsg_size;
> > - pdata.dump_oops = dump_oops;
> > + /* Parse deprecated module param "dump_oops" into "max_reason". */
> > + if (ramoops_dump_oops != -1)
> > + pdata.max_reason = ramoops_dump_oops ? KMSG_DUMP_OOPS
> > + : KMSG_DUMP_PANIC;
> > + pdata.max_reason = ramoops_max_reason;
>
> This isn't quite right. We're conditionally assigning pdata.max_reason
> and then immediately re-assigning it.
>
> IIUC, we're just missing an else block and it should look like this:
>
> /* Parse deprecated module param "dump_oops" into "max_reason". */
> if (ramoops_dump_oops != -1)
> pdata.max_reason = ramoops_dump_oops ? KMSG_DUMP_OOPS
> : KMSG_DUMP_PANIC;
> else
> pdata.max_reason = ramoops_max_reason;

Oops, yes. ramoops_max_reason needs to also have an "unset" value so
this can determine which was set... I'll get this fixed. Thanks for
double-checking this!

--
Kees Cook