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netfilter: x_tables: Use correct memory barriers.
[ Upstream commit175e476b8c
] When a new table value was assigned, it was followed by a write memory barrier. This ensured that all writes before this point would complete before any writes after this point. However, to determine whether the rules are unused, the sequence counter is read. To ensure that all writes have been done before these reads, a full memory barrier is needed, not just a write memory barrier. The same argument applies when incrementing the counter, before the rules are read. Changing to using smp_mb() instead of smp_wmb() fixes the kernel panic reported incc00bcaa58
(which is still present), while still maintaining the same speed of replacing tables. The smb_mb() barriers potentially slow the packet path, however testing has shown no measurable change in performance on a 4-core MIPS64 platform. Fixes:7f5c6d4f66
("netfilter: get rid of atomic ops in fast path") Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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2 changed files with 2 additions and 2 deletions
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@ -376,7 +376,7 @@ static inline unsigned int xt_write_recseq_begin(void)
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* since addend is most likely 1
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* since addend is most likely 1
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*/
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*/
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__this_cpu_add(xt_recseq.sequence, addend);
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__this_cpu_add(xt_recseq.sequence, addend);
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smp_wmb();
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smp_mb();
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return addend;
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return addend;
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}
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}
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@ -1389,7 +1389,7 @@ xt_replace_table(struct xt_table *table,
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table->private = newinfo;
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table->private = newinfo;
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/* make sure all cpus see new ->private value */
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/* make sure all cpus see new ->private value */
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smp_wmb();
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smp_mb();
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/*
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/*
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* Even though table entries have now been swapped, other CPU's
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* Even though table entries have now been swapped, other CPU's
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