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neighbour: Fix __randomize_layout crash in struct neighbour

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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 1ee60356c2 ("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: 1ee60356c2 ("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>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/ZWJoRsJGnCPdJ3+2@work
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Gustavo A. R. Silva 2023-11-25 15:33:58 -06:00 committed by Paolo Abeni
parent fd7f98b2e1
commit 45b3fae467
1 changed files with 1 additions and 1 deletions
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2
include/net/neighbour.h
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@ -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 {