| Message ID | 20230722231508.1030269-3-pasha.tatashin@soleen.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | page table check warn instead of panic | expand |
Hi-- On 7/22/23 16:15, Pasha Tatashin wrote: > The default behavior of page table check was changed from panicking > kernel to printing a warning. > > Add a note how to still panic the kernel when error is detected. > > Signed-off-by: Pasha Tatashin<pasha.tatashin@soleen.com> > --- > Documentation/mm/page_table_check.rst | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/Documentation/mm/page_table_check.rst b/Documentation/mm/page_table_check.rst > index c12838ce6b8d..f534c80ee9c9 100644 > --- a/Documentation/mm/page_table_check.rst > +++ b/Documentation/mm/page_table_check.rst > @@ -14,13 +14,14 @@ Page table check performs extra verifications at the time when new pages become > accessible from the userspace by getting their page table entries (PTEs PMDs > etc.) added into the table. > > -In case of detected corruption, the kernel is crashed. There is a small > +In case of detected corruption, a warning is printed. There is a small > performance and memory overhead associated with the page table check. Therefore, > it is disabled by default, but can be optionally enabled on systems where the > extra hardening outweighs the performance costs. Also, because page table check > is synchronous, it can help with debugging double map memory corruption issues, > by crashing kernel at the time wrong mapping occurs instead of later which is > -often the case with memory corruptions bugs. > +often the case with memory corruptions bugs. In order to crash kernel sysctl > +panic_on_warn should be set to 1. Better as: In order to crash the kernel, the sysctl panic_on_warn should be set to 1.
On Sat, Jul 22, 2023 at 7:59 PM Randy Dunlap <rdunlap@infradead.org> wrote: > > Hi-- > > On 7/22/23 16:15, Pasha Tatashin wrote: > > The default behavior of page table check was changed from panicking > > kernel to printing a warning. > > > > Add a note how to still panic the kernel when error is detected. > > > > Signed-off-by: Pasha Tatashin<pasha.tatashin@soleen.com> > > --- > > Documentation/mm/page_table_check.rst | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/mm/page_table_check.rst b/Documentation/mm/page_table_check.rst > > index c12838ce6b8d..f534c80ee9c9 100644 > > --- a/Documentation/mm/page_table_check.rst > > +++ b/Documentation/mm/page_table_check.rst > > @@ -14,13 +14,14 @@ Page table check performs extra verifications at the time when new pages become > > accessible from the userspace by getting their page table entries (PTEs PMDs > > etc.) added into the table. > > > > -In case of detected corruption, the kernel is crashed. There is a small > > +In case of detected corruption, a warning is printed. There is a small > > performance and memory overhead associated with the page table check. Therefore, > > it is disabled by default, but can be optionally enabled on systems where the > > extra hardening outweighs the performance costs. Also, because page table check > > is synchronous, it can help with debugging double map memory corruption issues, > > by crashing kernel at the time wrong mapping occurs instead of later which is > > -often the case with memory corruptions bugs. > > +often the case with memory corruptions bugs. In order to crash kernel sysctl > > +panic_on_warn should be set to 1. > > Better as: > In order to crash the kernel, the sysctl panic_on_warn should be set > to 1. Will update in the next version. Thanks, Pasha >
diff --git a/Documentation/mm/page_table_check.rst b/Documentation/mm/page_table_check.rst index c12838ce6b8d..f534c80ee9c9 100644 --- a/Documentation/mm/page_table_check.rst +++ b/Documentation/mm/page_table_check.rst @@ -14,13 +14,14 @@ Page table check performs extra verifications at the time when new pages become accessible from the userspace by getting their page table entries (PTEs PMDs etc.) added into the table. -In case of detected corruption, the kernel is crashed. There is a small +In case of detected corruption, a warning is printed. There is a small performance and memory overhead associated with the page table check. Therefore, it is disabled by default, but can be optionally enabled on systems where the extra hardening outweighs the performance costs. Also, because page table check is synchronous, it can help with debugging double map memory corruption issues, by crashing kernel at the time wrong mapping occurs instead of later which is -often the case with memory corruptions bugs. +often the case with memory corruptions bugs. In order to crash kernel sysctl +panic_on_warn should be set to 1. Double mapping detection logic ==============================
The default behavior of page table check was changed from panicking kernel to printing a warning. Add a note how to still panic the kernel when error is detected. Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> --- Documentation/mm/page_table_check.rst | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)