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[84.110.34.91]) by smtp.gmail.com with ESMTPSA id o26sm8510925wmc.33.2020.03.11.10.04.25 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 11 Mar 2020 10:04:25 -0700 (PDT) From: Basil Salman To: qemu-devel@nongnu.org, Michael Roth Subject: [PATCH v3 3/3] qga-win: prevent crash when executing guest-file-read with large count Date: Wed, 11 Mar 2020 19:04:17 +0200 Message-Id: <20200311170417.13415-4-basil@daynix.com> X-Mailer: git-send-email 2.17.2 In-Reply-To: <20200311170417.13415-1-basil@daynix.com> References: <20200311170417.13415-1-basil@daynix.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:4864:20::344 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yan Vugenfirer Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" BZ: #1594054 guest-file-read command is currently implemented to read from a file handle count number of bytes. when executed with a very large count number qemu-ga crashes. after some digging turns out that qemu-ga crashes after trying to allocate a buffer large enough to save the data read in it, the buffer was allocated using g_malloc0 which is not fail safe, and results a crash in case of failure. g_malloc0 was replaced with g_try_malloc0() which returns NULL on failure, A check was added for that case in order to prevent qemu-ga from crashing and to send a response to the qemu-ga client accordingly. Signed-off-by: Basil Salman --- qga/commands-win32.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/qga/commands-win32.c b/qga/commands-win32.c index 9c744d6405..b49920e201 100644 --- a/qga/commands-win32.c +++ b/qga/commands-win32.c @@ -343,7 +343,13 @@ GuestFileRead *qmp_guest_file_read(int64_t handle, bool has_count, } fh = gfh->fh; - buf = g_malloc0(count+1); + buf = g_try_malloc0(count + 1); + if (!buf) { + error_setg(errp, + "failed to allocate sufficient memory " + "to complete the requested service"); + return NULL; + } is_ok = ReadFile(fh, buf, count, &read_count, NULL); if (!is_ok) { error_setg_win32(errp, GetLastError(), "failed to read file"); -- 2.17.2