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AJvYcCWfrOP5VGFYVExfv0wYKOZS2JmzXYXhl9lMrmVVKlnS23YU6x9iQUuyeGV9bDCHP+zSEiyjgRI1wpbCMVE5EQSHcxRTMHl2G6fcLA== X-Gm-Message-State: AOJu0Yy0XJO/tYnuBNMKh20o+FAXQjUWHanr6IXGIrrBIY9I8ac4HYV2 dDZwVXT+UL72bb8xCnwI8yqGlMSc/zI4mxqWqyYY9A6Vv30GGcX5ZpA1+GwlZqQ= X-Google-Smtp-Source: AGHT+IGimyb61sKhw+mRuQVbC3bE2Obmy5HP7cvL4gIjsSjX8fXY+fkEjJOzQlmt3WtZxu0/FhFwCQ== X-Received: by 2002:a17:907:c7e2:b0:a7a:1d35:4106 with SMTP id a640c23a62f3a-a80aa557a83mr159871766b.5.1723215631262; Fri, 09 Aug 2024 08:00:31 -0700 (PDT) Received: from localhost ([196.207.164.177]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a7dc9bc3c6esm866125566b.15.2024.08.09.08.00.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Aug 2024 08:00:30 -0700 (PDT) Date: Fri, 9 Aug 2024 18:00:26 +0300 From: Dan Carpenter To: Su Hui , David Howells Cc: sfrench@samba.org, pc@manguebit.com, ronniesahlberg@gmail.com, sprasad@microsoft.com, tom@talpey.com, bharathsm@microsoft.com, nathan@kernel.org, ndesaulniers@google.com, morbo@google.com, justinstitt@google.com, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] smb/client: avoid possible NULL dereference in cifs_free_subrequest() Message-ID: <893f2ebb-2979-4e34-bdab-a7cbb0c7e7b8@stanley.mountain> References: <20240808122331.342473-1-suhui@nfschina.com> Precedence: bulk X-Mailing-List: linux-cifs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240808122331.342473-1-suhui@nfschina.com> On Thu, Aug 08, 2024 at 08:23:32PM +0800, Su Hui wrote: > Clang static checker (scan-build) warning: > cifsglob.h:line 890, column 3 > Access to field 'ops' results in a dereference of a null pointer. > > Commit 519be989717c ("cifs: Add a tracepoint to track credits involved in > R/W requests") adds a check for 'rdata->server', and let clang throw this > warning about NULL dereference. > > When 'rdata->credits.value != 0 && rdata->server == NULL' happens, > add_credits_and_wake_if() will call rdata->server->ops->add_credits(). > This will cause NULL dereference problem. Add a check for 'rdata->server' > to avoid NULL dereference. > > Signed-off-by: Su Hui Needs a Fixes tag. Also when you add a Fixes tag, then get_maintainer will add the David Howells automatically. I've added him manually. > --- > fs/smb/client/file.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c > index b2405dd4d4d4..45459af5044d 100644 > --- a/fs/smb/client/file.c > +++ b/fs/smb/client/file.c > @@ -315,7 +315,7 @@ static void cifs_free_subrequest(struct netfs_io_subrequest *subreq) > #endif > } > > - if (rdata->credits.value != 0) > + if (rdata->credits.value != 0) { > trace_smb3_rw_credits(rdata->rreq->debug_id, > rdata->subreq.debug_index, > rdata->credits.value, > @@ -323,8 +323,12 @@ static void cifs_free_subrequest(struct netfs_io_subrequest *subreq) > rdata->server ? rdata->server->in_flight : 0, > -rdata->credits.value, > cifs_trace_rw_credits_free_subreq); > + if (rdata->server) > + add_credits_and_wake_if(rdata->server, &rdata->credits, 0); > + else > + rdata->credits.value = 0; ^^^^^^^^^^^^^^^^^^^^^^^^^ Why do this? regards, dan carpenter