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Thu, 08 Feb 2024 05:45:55 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCV50/6hEH2oBM+iqhOHCBDYEPy0QZQMcC70huGD0sffG+xN8VTSw897VHodAGJNRVrGQBmCK/U/RY3PWlN1STLjhGQuXFE3 Received: from imac ([2a02:8010:60a0:0:4c4b:7e8e:f012:825c]) by smtp.gmail.com with ESMTPSA id e18-20020adffd12000000b0033b4acb999dsm3617430wrr.98.2024.02.08.05.45.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Feb 2024 05:45:55 -0800 (PST) From: Donald Hunter To: Maks Mishin Cc: Stephen Hemminger , netdev@vger.kernel.org Subject: Re: [PATCH] genl: Fix descriptor leak in get_genl_kind() In-Reply-To: <20240207200823.7229-1-maks.mishinFZ@gmail.com> (Maks Mishin's message of "Wed, 7 Feb 2024 23:08:23 +0300") Date: Thu, 08 Feb 2024 13:22:27 +0000 Message-ID: References: <20240207200823.7229-1-maks.mishinFZ@gmail.com> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Maks Mishin writes: > Signed-off-by: Maks Mishin The subject should say [PATCH iproute2] or [PATCH iproute2-next] since it targets that project. > --- > genl/genl.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/genl/genl.c b/genl/genl.c > index 85cc73bb..74100dad 100644 > --- a/genl/genl.c > +++ b/genl/genl.c > @@ -71,6 +71,9 @@ static struct genl_util *get_genl_kind(const char *str) > snprintf(buf, sizeof(buf), "%s_genl_util", str); > > f = dlsym(dlh, buf); > + if (dlh != NULL) > + dlclose(dlh); This is broken. If the earlier dlopen() actually loaded a .so then this dlclose() will close it again, before f gets used. When f gets dereferenced later, the program will crash. If this works at all, it is because dlopen(NULL, ...) returns a handle to the main program, so dlclose() doesn't unload it. My assumption is that the author is leaving resources to be released at program exit. It is a short-lived command line utility after all. > + > if (f == NULL) > goto noexist; > reg: