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[5.186.115.54]) by smtp.gmail.com with ESMTPSA id y2sm21140815wmy.2.2019.11.18.03.24.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Nov 2019 03:24:23 -0800 (PST) From: Rasmus Villemoes To: Qiang Zhao , Li Yang , Christophe Leroy Cc: linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Scott Wood , Timur Tabi , Rasmus Villemoes Subject: [PATCH v5 39/48] soc: fsl: qe: refactor cpm_muram_alloc_common to prevent BUG on error path Date: Mon, 18 Nov 2019 12:23:15 +0100 Message-Id: <20191118112324.22725-40-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191118112324.22725-1-linux@rasmusvillemoes.dk> References: <20191118112324.22725-1-linux@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the kmalloc() fails, we try to undo the gen_pool allocation we've just done. Unfortunately, start has already been modified to subtract the GENPOOL_OFFSET bias, so we're freeing something that very likely doesn't exist in the gen_pool, meaning we hit the kernel BUG at lib/genalloc.c:399! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM ... [<803fd0e8>] (gen_pool_free) from [<80426bc8>] (cpm_muram_alloc_common+0xb0/0xc8) [<80426bc8>] (cpm_muram_alloc_common) from [<80426c28>] (cpm_muram_alloc+0x48/0x80) [<80426c28>] (cpm_muram_alloc) from [<80428214>] (ucc_slow_init+0x110/0x4f0) [<80428214>] (ucc_slow_init) from [<8044a718>] (qe_uart_request_port+0x3c/0x1d8) (this was tested by just injecting a random failure by adding "|| (get_random_int()&7) == 0" to the "if (!entry)" condition). Refactor the code so we do the kmalloc() first, meaning that's the thing that needs undoing in case gen_pool_alloc_algo() then fails. This allows a later cleanup to move the locking from the callers into the _common function, keeping the kmalloc() out of the critical region and then, hopefully (if all the muram_alloc callers allow) change it to a GFP_KERNEL allocation. Signed-off-by: Rasmus Villemoes --- drivers/soc/fsl/qe/qe_common.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/soc/fsl/qe/qe_common.c b/drivers/soc/fsl/qe/qe_common.c index dcb267567d76..a81a1a79f1ca 100644 --- a/drivers/soc/fsl/qe/qe_common.c +++ b/drivers/soc/fsl/qe/qe_common.c @@ -119,23 +119,21 @@ static s32 cpm_muram_alloc_common(unsigned long size, struct muram_block *entry; s32 start; + entry = kmalloc(sizeof(*entry), GFP_ATOMIC); + if (!entry) + return -ENOMEM; start = gen_pool_alloc_algo(muram_pool, size, algo, data); - if (!start) - goto out2; + if (!start) { + kfree(entry); + return -ENOMEM; + } start = start - GENPOOL_OFFSET; memset_io(cpm_muram_addr(start), 0, size); - entry = kmalloc(sizeof(*entry), GFP_ATOMIC); - if (!entry) - goto out1; entry->start = start; entry->size = size; list_add(&entry->head, &muram_block_list); return start; -out1: - gen_pool_free(muram_pool, start, size); -out2: - return -ENOMEM; } /* -- 2.23.0