| Message ID | 20240302001714.674091-6-rick.p.edgecombe@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
On 3/2/24 01:17, Rick Edgecombe wrote: > Future changes will need to add a new member to struct > vm_unmapped_area_info. This would cause trouble for any call site that > doesn't initialize the struct. Currently every caller sets each field > manually, so if new fields are added they will be unitialized and the core > code parsing the struct will see garbage in the new field. > > It could be possible to initialize the new field manually to 0 at each > call site. This and a couple other options were discussed, and the > consensus (see links) was that in general the best way to accomplish this > would be via static initialization with designated field initiators. > Having some struct vm_unmapped_area_info instances not zero initialized > will put those sites at risk of feeding garbage into vm_unmapped_area() if > the convention is to zero initialize the struct and any new field addition > misses a call site that initializes each field manually. > > It could be possible to leave the code mostly untouched, and just change > the line: > struct vm_unmapped_area_info info > to: > struct vm_unmapped_area_info info = {}; > > However, that would leave cleanup for the fields that are manually set > to zero, as it would no longer be required. > > So to be reduce the chance of bugs via uninitialized fields, instead > simply continue the process to initialize the struct this way tree wide. > This will zero any unspecified members. Move the field initializers to the > struct declaration when they are known at that time. Leave the fields out > that were manually initialized to zero, as this would be redundant for > designated initializers. > > Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> > Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> > Cc: Helge Deller <deller@gmx.de> Acked-by: Helge Deller <deller@gmx.de> Thanks! Helge > Cc: linux-parisc@vger.kernel.org > Link: https://lore.kernel.org/lkml/202402280912.33AEE7A9CF@keescook/#t > Link: https://lore.kernel.org/lkml/j7bfvig3gew3qruouxrh7z7ehjjafrgkbcmg6tcghhfh3rhmzi@wzlcoecgy5rs/ > --- > Hi, > > This patch was split and refactored out of a tree-wide change [0] to just > zero-init each struct vm_unmapped_area_info. The overall goal of the > series is to help shadow stack guard gaps. Currently, there is only one > arch with shadow stacks, but two more are in progress. It is 0day tested > only. > > Thanks, > > Rick > > [0] https://lore.kernel.org/lkml/20240226190951.3240433-6-rick.p.edgecombe@intel.com/ > --- > arch/parisc/kernel/sys_parisc.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c > index 98af719d5f85..1f0b60766aac 100644 > --- a/arch/parisc/kernel/sys_parisc.c > +++ b/arch/parisc/kernel/sys_parisc.c > @@ -104,7 +104,9 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp, > struct vm_area_struct *vma, *prev; > unsigned long filp_pgoff; > int do_color_align; > - struct vm_unmapped_area_info info; > + struct vm_unmapped_area_info info = { > + .length = len > + }; > > if (unlikely(len > TASK_SIZE)) > return -ENOMEM; > @@ -139,7 +141,6 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp, > return addr; > } > > - info.length = len; > info.align_mask = do_color_align ? (PAGE_MASK & (SHM_COLOUR - 1)) : 0; > info.align_offset = shared_align_offset(filp_pgoff, pgoff); >
On Sat, 2024-03-02 at 07:35 +0100, Helge Deller wrote:
> Acked-by: Helge Deller <deller@gmx.de>
Thanks!
diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c index 98af719d5f85..1f0b60766aac 100644 --- a/arch/parisc/kernel/sys_parisc.c +++ b/arch/parisc/kernel/sys_parisc.c @@ -104,7 +104,9 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp, struct vm_area_struct *vma, *prev; unsigned long filp_pgoff; int do_color_align; - struct vm_unmapped_area_info info; + struct vm_unmapped_area_info info = { + .length = len + }; if (unlikely(len > TASK_SIZE)) return -ENOMEM; @@ -139,7 +141,6 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp, return addr; } - info.length = len; info.align_mask = do_color_align ? (PAGE_MASK & (SHM_COLOUR - 1)) : 0; info.align_offset = shared_align_offset(filp_pgoff, pgoff);
Future changes will need to add a new member to struct vm_unmapped_area_info. This would cause trouble for any call site that doesn't initialize the struct. Currently every caller sets each field manually, so if new fields are added they will be unitialized and the core code parsing the struct will see garbage in the new field. It could be possible to initialize the new field manually to 0 at each call site. This and a couple other options were discussed, and the consensus (see links) was that in general the best way to accomplish this would be via static initialization with designated field initiators. Having some struct vm_unmapped_area_info instances not zero initialized will put those sites at risk of feeding garbage into vm_unmapped_area() if the convention is to zero initialize the struct and any new field addition misses a call site that initializes each field manually. It could be possible to leave the code mostly untouched, and just change the line: struct vm_unmapped_area_info info to: struct vm_unmapped_area_info info = {}; However, that would leave cleanup for the fields that are manually set to zero, as it would no longer be required. So to be reduce the chance of bugs via uninitialized fields, instead simply continue the process to initialize the struct this way tree wide. This will zero any unspecified members. Move the field initializers to the struct declaration when they are known at that time. Leave the fields out that were manually initialized to zero, as this would be redundant for designated initializers. Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Helge Deller <deller@gmx.de> Cc: linux-parisc@vger.kernel.org Link: https://lore.kernel.org/lkml/202402280912.33AEE7A9CF@keescook/#t Link: https://lore.kernel.org/lkml/j7bfvig3gew3qruouxrh7z7ehjjafrgkbcmg6tcghhfh3rhmzi@wzlcoecgy5rs/ --- Hi, This patch was split and refactored out of a tree-wide change [0] to just zero-init each struct vm_unmapped_area_info. The overall goal of the series is to help shadow stack guard gaps. Currently, there is only one arch with shadow stacks, but two more are in progress. It is 0day tested only. Thanks, Rick [0] https://lore.kernel.org/lkml/20240226190951.3240433-6-rick.p.edgecombe@intel.com/ --- arch/parisc/kernel/sys_parisc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)