| Message ID | 20210727205855.411487-48-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Johannes Berg |
| Headers | show |
| Series | Introduce strict memcpy() bounds checking | expand |
On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote: > In preparation for FORTIFY_SOURCE performing compile-time and run-time > field bounds checking for memset(), avoid intentionally writing across > neighboring fields. > > Use memset_after() so memset() doesn't get confused about writing > beyond the destination member that is intended to be the starting point > of zeroing through the end of the struct. > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > fs/btrfs/root-tree.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c > index 702dc5441f03..ec9e78f65fca 100644 > --- a/fs/btrfs/root-tree.c > +++ b/fs/btrfs/root-tree.c > @@ -39,10 +39,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot, > need_reset = 1; > } > if (need_reset) { > - memset(&item->generation_v2, 0, > - sizeof(*item) - offsetof(struct btrfs_root_item, > - generation_v2)); > - Please add /* Clear all members from generation_v2 onwards */ > + memset_after(item, 0, level); > generate_random_guid(item->uuid); Acked-by: David Sterba <dsterba@suse.com>
On Wed, Jul 28, 2021 at 11:42:15AM +0200, David Sterba wrote: > On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote: > > In preparation for FORTIFY_SOURCE performing compile-time and run-time > > field bounds checking for memset(), avoid intentionally writing across > > neighboring fields. > > > > Use memset_after() so memset() doesn't get confused about writing > > beyond the destination member that is intended to be the starting point > > of zeroing through the end of the struct. > > > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > fs/btrfs/root-tree.c | 5 +---- > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c > > index 702dc5441f03..ec9e78f65fca 100644 > > --- a/fs/btrfs/root-tree.c > > +++ b/fs/btrfs/root-tree.c > > @@ -39,10 +39,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot, > > need_reset = 1; > > } > > if (need_reset) { > > - memset(&item->generation_v2, 0, > > - sizeof(*item) - offsetof(struct btrfs_root_item, > > - generation_v2)); > > - > > Please add > /* Clear all members from generation_v2 onwards */ > > > + memset_after(item, 0, level); Perhaps there should be another helper memset_starting()? That would make these cases a bit more self-documenting. + memset_starting(item, 0, generation_v2); > > generate_random_guid(item->uuid); > > Acked-by: David Sterba <dsterba@suse.com> What do you think? -Kees
On Wed, Jul 28, 2021 at 02:56:31PM -0700, Kees Cook wrote: > On Wed, Jul 28, 2021 at 11:42:15AM +0200, David Sterba wrote: > > On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote: > > > In preparation for FORTIFY_SOURCE performing compile-time and run-time > > > field bounds checking for memset(), avoid intentionally writing across > > > neighboring fields. > > > > > > Use memset_after() so memset() doesn't get confused about writing > > > beyond the destination member that is intended to be the starting point > > > of zeroing through the end of the struct. > > > > > > Signed-off-by: Kees Cook <keescook@chromium.org> > > > --- > > > fs/btrfs/root-tree.c | 5 +---- > > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > > > diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c > > > index 702dc5441f03..ec9e78f65fca 100644 > > > --- a/fs/btrfs/root-tree.c > > > +++ b/fs/btrfs/root-tree.c > > > @@ -39,10 +39,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot, > > > need_reset = 1; > > > } > > > if (need_reset) { > > > - memset(&item->generation_v2, 0, > > > - sizeof(*item) - offsetof(struct btrfs_root_item, > > > - generation_v2)); > > > - > > > > Please add > > /* Clear all members from generation_v2 onwards */ > > > > > + memset_after(item, 0, level); > > Perhaps there should be another helper memset_starting()? That would > make these cases a bit more self-documenting. That would be better, yes. > + memset_starting(item, 0, generation_v2); memset_from?
On Thu, Jul 29, 2021 at 12:33:37PM +0200, David Sterba wrote: > On Wed, Jul 28, 2021 at 02:56:31PM -0700, Kees Cook wrote: > > On Wed, Jul 28, 2021 at 11:42:15AM +0200, David Sterba wrote: > > > On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote: > > > > In preparation for FORTIFY_SOURCE performing compile-time and run-time > > > > field bounds checking for memset(), avoid intentionally writing across > > > > neighboring fields. > > > > > > > > Use memset_after() so memset() doesn't get confused about writing > > > > beyond the destination member that is intended to be the starting point > > > > of zeroing through the end of the struct. > > > > > > > > Signed-off-by: Kees Cook <keescook@chromium.org> > > > > --- > > > > fs/btrfs/root-tree.c | 5 +---- > > > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > > > > > diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c > > > > index 702dc5441f03..ec9e78f65fca 100644 > > > > --- a/fs/btrfs/root-tree.c > > > > +++ b/fs/btrfs/root-tree.c > > > > @@ -39,10 +39,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot, > > > > need_reset = 1; > > > > } > > > > if (need_reset) { > > > > - memset(&item->generation_v2, 0, > > > > - sizeof(*item) - offsetof(struct btrfs_root_item, > > > > - generation_v2)); > > > > - > > > > > > Please add > > > /* Clear all members from generation_v2 onwards */ > > > > > > > + memset_after(item, 0, level); > > > > Perhaps there should be another helper memset_starting()? That would > > make these cases a bit more self-documenting. > > That would be better, yes. > > > + memset_starting(item, 0, generation_v2); > > memset_from? For v2, I bikeshed this to "memset_startat" since "from" is semantically close to "source" which I thought might be confusing. (I, too, did not like "starting".) :) Can I make "bikeshed" a verb? :P
On Sat, Jul 31, 2021 at 08:25:51AM -0700, Kees Cook wrote: > On Thu, Jul 29, 2021 at 12:33:37PM +0200, David Sterba wrote: > > On Wed, Jul 28, 2021 at 02:56:31PM -0700, Kees Cook wrote: > > > On Wed, Jul 28, 2021 at 11:42:15AM +0200, David Sterba wrote: > > > > On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote: > > > > > } > > > > > if (need_reset) { > > > > > - memset(&item->generation_v2, 0, > > > > > - sizeof(*item) - offsetof(struct btrfs_root_item, > > > > > - generation_v2)); > > > > > - > > > > > > > > Please add > > > > /* Clear all members from generation_v2 onwards */ > > > > > > > > > + memset_after(item, 0, level); > > > > > > Perhaps there should be another helper memset_starting()? That would > > > make these cases a bit more self-documenting. > > > > That would be better, yes. > > > > > + memset_starting(item, 0, generation_v2); > > > > memset_from? > > For v2, I bikeshed this to "memset_startat" since "from" is semantically > close to "source" which I thought might be confusing. (I, too, did not > like "starting".) :) memset_startat works for me, thanks.
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c index 702dc5441f03..ec9e78f65fca 100644 --- a/fs/btrfs/root-tree.c +++ b/fs/btrfs/root-tree.c @@ -39,10 +39,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot, need_reset = 1; } if (need_reset) { - memset(&item->generation_v2, 0, - sizeof(*item) - offsetof(struct btrfs_root_item, - generation_v2)); - + memset_after(item, 0, level); generate_random_guid(item->uuid); } }
In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memset(), avoid intentionally writing across neighboring fields. Use memset_after() so memset() doesn't get confused about writing beyond the destination member that is intended to be the starting point of zeroing through the end of the struct. Signed-off-by: Kees Cook <keescook@chromium.org> --- fs/btrfs/root-tree.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)