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Bottomley" , Helge Deller , Arnd Bergmann , Kees Cook , Greg Kroah-Hartman Subject: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location() Date: Thu, 14 Oct 2021 07:50:01 +0200 Message-Id: X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1634190596; l=3389; s=20211009; h=from:subject:message-id; bh=/NBloWboE7tAULPmP7BOXtz6OWoNUEZRrAB3xKixwdU=; b=4flPamtTkvGPUtcU0sHwSxv0NG8ktt3lwWa8/xTZBJ5IOlZl9vgP0rMEQGn4vB7FTUGMNKDCY1vl jjnZDPU5Bkp23Hqfy/0Db4Tf8vg3xiRSXNuPYEhC+6C4yEdRDVTL X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" execute_location() and execute_user_location() intent to copy do_nothing() text and execute it at a new location. However, at the time being it doesn't copy do_nothing() function but do_nothing() function descriptor which still points to the original text. So at the end it still executes do_nothing() at its original location allthough using a copied function descriptor. So, fix that by really copying do_nothing() text and build a new function descriptor by copying do_nothing() function descriptor and updating the target address with the new location. Also fix the displayed addresses by dereferencing do_nothing() function descriptor. Signed-off-by: Christophe Leroy --- drivers/misc/lkdtm/perms.c | 25 +++++++++++++++++++++---- include/asm-generic/sections.h | 5 +++++ 2 files changed, 26 insertions(+), 4 deletions(-) diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 5266dc28df6e..96b3ebfcb8ed 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -44,19 +44,32 @@ static noinline void do_overwritten(void) return; } +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst) +{ + memcpy(fdesc, do_nothing, sizeof(*fdesc)); + fdesc->addr = (unsigned long)dst; + barrier(); + + return fdesc; +} + static noinline void execute_location(void *dst, bool write) { void (*func)(void) = dst; + func_desc_t fdesc; + void *do_nothing_text = dereference_function_descriptor(do_nothing); - pr_info("attempting ok execution at %px\n", do_nothing); + pr_info("attempting ok execution at %px\n", do_nothing_text); do_nothing(); if (write == CODE_WRITE) { - memcpy(dst, do_nothing, EXEC_SIZE); + memcpy(dst, do_nothing_text, EXEC_SIZE); flush_icache_range((unsigned long)dst, (unsigned long)dst + EXEC_SIZE); } pr_info("attempting bad execution at %px\n", func); + if (have_function_descriptors()) + func = setup_function_descriptor(&fdesc, dst); func(); pr_err("FAIL: func returned\n"); } @@ -67,15 +80,19 @@ static void execute_user_location(void *dst) /* Intentionally crossing kernel/user memory boundary. */ void (*func)(void) = dst; + func_desc_t fdesc; + void *do_nothing_text = dereference_function_descriptor(do_nothing); - pr_info("attempting ok execution at %px\n", do_nothing); + pr_info("attempting ok execution at %px\n", do_nothing_text); do_nothing(); - copied = access_process_vm(current, (unsigned long)dst, do_nothing, + copied = access_process_vm(current, (unsigned long)dst, do_nothing_text, EXEC_SIZE, FOLL_WRITE); if (copied < EXEC_SIZE) return; pr_info("attempting bad execution at %px\n", func); + if (have_function_descriptors()) + func = setup_function_descriptor(&fdesc, dst); func(); pr_err("FAIL: func returned\n"); } diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index 76163883c6ff..d225318538bd 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -70,6 +70,11 @@ typedef struct { } func_desc_t; #endif +static inline bool have_function_descriptors(void) +{ + return __is_defined(HAVE_FUNCTION_DESCRIPTORS); +} + /* random extra sections (if any). Override * in asm/sections.h */ #ifndef arch_is_kernel_text -- 2.31.1