| Message ID | ZWJoRsJGnCPdJ3+2@work (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 45b3fae4675dc1d4ee2d7aefa19d85ee4f891377 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | neighbour: Fix __randomize_layout crash in struct neighbour | expand |
On Sat, Nov 25, 2023 at 03:33:58PM -0600, Gustavo A. R. Silva wrote: > Previously, one-element and zero-length arrays were treated as true > flexible arrays, even though they are actually "fake" flex arrays. > The __randomize_layout would leave them untouched at the end of the > struct, similarly to proper C99 flex-array members. > > However, this approach changed with commit 1ee60356c2dc ("gcc-plugins: > randstruct: Only warn about true flexible arrays"). Now, only C99 > flexible-array members will remain untouched at the end of the struct, > while one-element and zero-length arrays will be subject to randomization. > > Fix a `__randomize_layout` crash in `struct neighbour` by transforming > zero-length array `primary_key` into a proper C99 flexible-array member. > > Fixes: 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible arrays") > Closes: https://lore.kernel.org/linux-hardening/20231124102458.GB1503258@e124191.cambridge.arm.com/ > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Yes, please. Do we have any other 0-sized arrays hiding out in the kernel? We need to get these all cleared... Reviewed-by: Kees Cook <keescook@chromium.org>
On 11/27/23 18:29, Kees Cook wrote: > On Sat, Nov 25, 2023 at 03:33:58PM -0600, Gustavo A. R. Silva wrote: >> Previously, one-element and zero-length arrays were treated as true >> flexible arrays, even though they are actually "fake" flex arrays. >> The __randomize_layout would leave them untouched at the end of the >> struct, similarly to proper C99 flex-array members. >> >> However, this approach changed with commit 1ee60356c2dc ("gcc-plugins: >> randstruct: Only warn about true flexible arrays"). Now, only C99 >> flexible-array members will remain untouched at the end of the struct, >> while one-element and zero-length arrays will be subject to randomization. >> >> Fix a `__randomize_layout` crash in `struct neighbour` by transforming >> zero-length array `primary_key` into a proper C99 flexible-array member. >> >> Fixes: 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible arrays") >> Closes: https://lore.kernel.org/linux-hardening/20231124102458.GB1503258@e124191.cambridge.arm.com/ >> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > > Yes, please. Do we have any other 0-sized arrays hiding out in the > kernel? We need to get these all cleared... I've found 27 instances of zero-length fake-flex arrays in next-20231127. I'll send a patch series to transform all of them. > > Reviewed-by: Kees Cook <keescook@chromium.org> > Thanks! -- Gustavo
Hi, On Sat, Nov 25, 2023 at 03:33:58PM -0600, Gustavo A. R. Silva wrote: > Previously, one-element and zero-length arrays were treated as true > flexible arrays, even though they are actually "fake" flex arrays. > The __randomize_layout would leave them untouched at the end of the > struct, similarly to proper C99 flex-array members. > > However, this approach changed with commit 1ee60356c2dc ("gcc-plugins: > randstruct: Only warn about true flexible arrays"). Now, only C99 > flexible-array members will remain untouched at the end of the struct, > while one-element and zero-length arrays will be subject to randomization. > > Fix a `__randomize_layout` crash in `struct neighbour` by transforming > zero-length array `primary_key` into a proper C99 flexible-array member. > > Fixes: 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible arrays") > Closes: https://lore.kernel.org/linux-hardening/20231124102458.GB1503258@e124191.cambridge.arm.com/ > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- > include/net/neighbour.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/net/neighbour.h b/include/net/neighbour.h > index 07022bb0d44d..0d28172193fa 100644 > --- a/include/net/neighbour.h > +++ b/include/net/neighbour.h > @@ -162,7 +162,7 @@ struct neighbour { > struct rcu_head rcu; > struct net_device *dev; > netdevice_tracker dev_tracker; > - u8 primary_key[0]; > + u8 primary_key[]; > } __randomize_layout; > > struct neigh_ops { Fixes the crash for me! Tested-by: Joey Gouly <joey.gouly@arm.com>
Hello: This patch was applied to netdev/net.git (main) by Paolo Abeni <pabeni@redhat.com>: On Sat, 25 Nov 2023 15:33:58 -0600 you wrote: > Previously, one-element and zero-length arrays were treated as true > flexible arrays, even though they are actually "fake" flex arrays. > The __randomize_layout would leave them untouched at the end of the > struct, similarly to proper C99 flex-array members. > > However, this approach changed with commit 1ee60356c2dc ("gcc-plugins: > randstruct: Only warn about true flexible arrays"). Now, only C99 > flexible-array members will remain untouched at the end of the struct, > while one-element and zero-length arrays will be subject to randomization. > > [...] Here is the summary with links: - neighbour: Fix __randomize_layout crash in struct neighbour https://git.kernel.org/netdev/net/c/45b3fae4675d You are awesome, thank you!
>> diff --git a/include/net/neighbour.h b/include/net/neighbour.h >> index 07022bb0d44d..0d28172193fa 100644 >> --- a/include/net/neighbour.h >> +++ b/include/net/neighbour.h >> @@ -162,7 +162,7 @@ struct neighbour { >> struct rcu_head rcu; >> struct net_device *dev; >> netdevice_tracker dev_tracker; >> - u8 primary_key[0]; >> + u8 primary_key[]; >> } __randomize_layout; >> >> struct neigh_ops { > > Fixes the crash for me! Awesome. :) -- Gustavo
diff --git a/include/net/neighbour.h b/include/net/neighbour.h index 07022bb0d44d..0d28172193fa 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -162,7 +162,7 @@ struct neighbour { struct rcu_head rcu; struct net_device *dev; netdevice_tracker dev_tracker; - u8 primary_key[0]; + u8 primary_key[]; } __randomize_layout; struct neigh_ops {
Previously, one-element and zero-length arrays were treated as true flexible arrays, even though they are actually "fake" flex arrays. The __randomize_layout would leave them untouched at the end of the struct, similarly to proper C99 flex-array members. However, this approach changed with commit 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible arrays"). Now, only C99 flexible-array members will remain untouched at the end of the struct, while one-element and zero-length arrays will be subject to randomization. Fix a `__randomize_layout` crash in `struct neighbour` by transforming zero-length array `primary_key` into a proper C99 flexible-array member. Fixes: 1ee60356c2dc ("gcc-plugins: randstruct: Only warn about true flexible arrays") Closes: https://lore.kernel.org/linux-hardening/20231124102458.GB1503258@e124191.cambridge.arm.com/ Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- include/net/neighbour.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)