The patch titled Subject: mm: zswap: fix crypto_free_acomp deadlock in zswap_cpu_comp_dead has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-zswap-fix-crypto_free_acomp-deadlock-in-zswap_cpu_comp_dead.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Herbert Xu herbert@gondor.apana.org.au Subject: mm: zswap: fix crypto_free_acomp deadlock in zswap_cpu_comp_dead Date: Tue, 25 Feb 2025 16:53:58 +0800
Call crypto_free_acomp outside of the mutex in zswap_cpu_comp_dead() as otherwise this could deadlock as the allocation path may lead back into zswap while holding the same lock. Zap the pointers to acomp and buffer after freeing.
Also move the NULL check on acomp_ctx so that it takes place before the mutex dereference.
Link: https://lkml.kernel.org/r/Z72FJnbA39zWh4zS@gondor.apana.org.au Fixes: 12dcb0ef5406 ("mm: zswap: properly synchronize freeing resources during CPU hotunplug") Reported-by: syzbot+1a517ccfcbc6a7ab0f82@syzkaller.appspotmail.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Cc: David S. Miller davem@davemloft.net Cc: Yosry Ahmed yosry.ahmed@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/zswap.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-)
--- a/mm/zswap.c~mm-zswap-fix-crypto_free_acomp-deadlock-in-zswap_cpu_comp_dead +++ a/mm/zswap.c @@ -881,18 +881,23 @@ static int zswap_cpu_comp_dead(unsigned { struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); + struct crypto_acomp *acomp = NULL; + + if (IS_ERR_OR_NULL(acomp_ctx)) + return 0;
mutex_lock(&acomp_ctx->mutex); - if (!IS_ERR_OR_NULL(acomp_ctx)) { - if (!IS_ERR_OR_NULL(acomp_ctx->req)) - acomp_request_free(acomp_ctx->req); - acomp_ctx->req = NULL; - if (!IS_ERR_OR_NULL(acomp_ctx->acomp)) - crypto_free_acomp(acomp_ctx->acomp); - kfree(acomp_ctx->buffer); - } + if (!IS_ERR_OR_NULL(acomp_ctx->req)) + acomp_request_free(acomp_ctx->req); + acomp_ctx->req = NULL; + acomp = acomp_ctx->acomp; + acomp_ctx->acomp = NULL; + kfree(acomp_ctx->buffer); + acomp_ctx->buffer = NULL; mutex_unlock(&acomp_ctx->mutex);
+ crypto_free_acomp(acomp); + return 0; }
_
Patches currently in -mm which might be from herbert@gondor.apana.org.au are
mm-zswap-fix-crypto_free_acomp-deadlock-in-zswap_cpu_comp_dead.patch