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Sun, 22 Sep 2019 05:33:23 +0000 From: Chaitanya Kulkarni To: Sagi Grimberg , "linux-nvme@lists.infradead.org" Subject: Re: [PATCH 1/2] scatterlist: make sgl_free null pointer safe Thread-Topic: [PATCH 1/2] scatterlist: make sgl_free null pointer safe Thread-Index: AQHVb9/Nml9ko61kuUmCZf1rz5rqAA== Date: Sun, 22 Sep 2019 05:33:23 +0000 Message-ID: References: <20190920181818.14424-1-sagi@grimberg.me> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Chaitanya.Kulkarni@wdc.com; x-originating-ip: [199.255.44.170] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: a4db592e-92ff-48fc-016f-08d73f1e6300 x-ms-office365-filtering-ht: Tenant x-microsoft-antispam: BCL:0; PCL:0; RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600167)(711020)(4605104)(1401327)(4618075)(2017052603328)(7193020); SRVR:BYAPR04MB6102; x-ms-traffictypediagnostic: BYAPR04MB6102: x-microsoft-antispam-prvs: wdcipoutbound: EOP-TRUE x-ms-oob-tlc-oobclassifiers: OLM:200; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org Unless I totally missed what you are trying to fix here, I think this case is already handled implicitly to avoid the code repetition inside for_each_sg() which makes :- sgl_free() sgl_free_order() sgl_free_n_order() code path NULL safe. I did a quick test without applying your patch with some prints and it worked file following module:- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include int init_module(void) { sgl_free(NULL); return 0; } void cleanup_module(void) { } MODULE_LICENSE("GPL"); MODULE_VERSION("1.0"); Prints :- diff --git a/lib/scatterlist.c b/lib/scatterlist.c index c2cf2c3..56fa586 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -563,13 +563,20 @@ void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) struct page *page; int i; + pr_info("%s %d\n", __func__, __LINE__); for_each_sg(sgl, sg, nents, i) { + pr_info("%s %d\n", __func__, __LINE__); if (!sg) break; + + pr_info("%s %d\n", __func__, __LINE__); page = sg_page(sg); if (page) __free_pages(page, order); + pr_info("%s %d\n", __func__, __LINE__); } + + pr_info("%s %d\n", __func__, __LINE__); kfree(sgl); } EXPORT_SYMBOL(sgl_free_n_order); @@ -581,6 +588,7 @@ void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) */ void sgl_free_order(struct scatterlist *sgl, int order) { + pr_info("%s %d\n", __func__, __LINE__); sgl_free_n_order(sgl, INT_MAX, order); } EXPORT_SYMBOL(sgl_free_order); @@ -591,6 +599,7 @@ void sgl_free_order(struct scatterlist *sgl, int order) */ void sgl_free(struct scatterlist *sgl) { + pr_info("%s %d\n", __func__, __LINE__); sgl_free_order(sgl, 0); } EXPORT_SYMBOL(sgl_free); Got the following output without any crash or warning :- [ 156.950073] sgl_free 602 [ 156.950076] sgl_free_order 591 [ 156.950078] sgl_free_n_order 566 [ 156.950079] sgl_free_n_order 568 [ 156.950081] sgl_free_n_order 579 Did I miss anything ? On 09/20/2019 11:18 AM, Sagi Grimberg wrote: > Match other alloc/free routines by checking the sgl pointer first. > > Signed-off-by: Sagi Grimberg > --- > lib/scatterlist.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index c2cf2c311b7d..fea25b035e67 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -563,6 +563,9 @@ void sgl_free_n_order(struct scatterlist *sgl, int nents, int order) > struct page *page; > int i; > > + if (!sgl) > + return; > + > for_each_sg(sgl, sg, nents, i) { > if (!sg) > break; > _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme