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Tue, 1 Aug 2023 16:09:48 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.93]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 87D604024F83; Tue, 1 Aug 2023 16:09:47 +0000 (UTC) Date: Tue, 1 Aug 2023 17:09:45 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Helge Deller Cc: Laurent Vivier , Richard Henderson , qemu-devel@nongnu.org Subject: Re: [PATCH] linux-user: Fix openat() emulation to correctly detect accesses to /proc Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Aug 01, 2023 at 04:58:57PM +0200, Helge Deller wrote: > In qemu we catch accesses to files like /proc/cpuinfo or /proc/net/route > and return to the guest contents which would be visible on a real system > (instead what the host would show). > > This patch fixes a bug, where for example the accesses > cat /proc////cpuinfo > or > cd /proc && cat cpuinfo > will not be recognized by qemu and where qemu will wrongly show > the contents of the host's /proc/cpuinfo file. > > Signed-off-by: Helge Deller > > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > index 917c388073..bb864c2bb3 100644 > --- a/linux-user/syscall.c > +++ b/linux-user/syscall.c > @@ -8531,9 +8531,11 @@ static int open_cpuinfo(CPUArchState *cpu_env, int fd) > } > #endif > > -int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, > +int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname, > int flags, mode_t mode, bool safe) > { > + char proc_name[PATH_MAX]; No PATH_MAX buffers declared on the stack please. > + const char *pathname; > struct fake_open { > const char *filename; > int (*fill)(CPUArchState *cpu_env, int fd); > @@ -8560,6 +8562,13 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, > { NULL, NULL, NULL } > }; > > + /* if this is a file from /proc/ filesystem, expand full name */ > + if (realpath(fname, proc_name) && strncmp(proc_name, "/proc/", 6) == 0) { QEMU relies on the extended semantics of realpath() where passing NULL for 'proc_name' causes it to allocate a buffer of the correct size and return the new buffer. Using that avoids PATH_MAX variables. > + pathname = proc_name; > + } else { > + pathname = fname; > + } With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|