From: Kees Cook keescook@chromium.org
[ Upstream commit 9e4bf6a08d1e127bcc4bd72557f2dfafc6bc7f41 ]
Since "dev_search_path" can technically be as large as PATH_MAX, there was a risk of truncation when copying it and a second string into "full_path" since it was also PATH_MAX sized. The W=1 builds were reporting this warning:
drivers/block/rnbd/rnbd-srv.c: In function 'process_msg_open.isra': drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095 [-Wformat-truncation=] 616 | snprintf(full_path, PATH_MAX, "%s/%s", | ^~ In function 'rnbd_srv_get_full_path', inlined from 'process_msg_open.isra' at drivers/block/rnbd/rnbd-srv.c:721:14: drivers/block/rnbd/rnbd-srv.c:616:17: note: 'snprintf' output between 2 and 4351 bytes into a destination of size 4096 616 | snprintf(full_path, PATH_MAX, "%s/%s", | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 617 | dev_search_path, dev_name); | ~~~~~~~~~~~~~~~~~~~~~~~~~~
To fix this, unconditionally check for truncation (as was already done for the case where "%SESSNAME%" was present).
Reported-by: kernel test robot lkp@intel.com Closes: https://lore.kernel.org/oe-kbuild-all/202312100355.lHoJPgKy-lkp@intel.com/ Cc: Md. Haris Iqbal haris.iqbal@ionos.com Cc: Jack Wang jinpu.wang@ionos.com Cc: Jens Axboe axboe@kernel.dk Cc: linux-block@vger.kernel.org Signed-off-by: Kees Cook keescook@chromium.org Acked-by: Guoqing Jiang guoqing.jiang@linux.dev Acked-by: Jack Wang jinpu.wang@ionos.com Link: https://lore.kernel.org/r/20231212214738.work.169-kees@kernel.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/block/rnbd/rnbd-srv.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c index e1bc8b4cd592..9c5d52335e17 100644 --- a/drivers/block/rnbd/rnbd-srv.c +++ b/drivers/block/rnbd/rnbd-srv.c @@ -591,6 +591,7 @@ static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess, { char *full_path; char *a, *b; + int len;
full_path = kmalloc(PATH_MAX, GFP_KERNEL); if (!full_path) @@ -602,19 +603,19 @@ static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess, */ a = strnstr(dev_search_path, "%SESSNAME%", sizeof(dev_search_path)); if (a) { - int len = a - dev_search_path; + len = a - dev_search_path;
len = snprintf(full_path, PATH_MAX, "%.*s/%s/%s", len, dev_search_path, srv_sess->sessname, dev_name); - if (len >= PATH_MAX) { - pr_err("Too long path: %s, %s, %s\n", - dev_search_path, srv_sess->sessname, dev_name); - kfree(full_path); - return ERR_PTR(-EINVAL); - } } else { - snprintf(full_path, PATH_MAX, "%s/%s", - dev_search_path, dev_name); + len = snprintf(full_path, PATH_MAX, "%s/%s", + dev_search_path, dev_name); + } + if (len >= PATH_MAX) { + pr_err("Too long path: %s, %s, %s\n", + dev_search_path, srv_sess->sessname, dev_name); + kfree(full_path); + return ERR_PTR(-EINVAL); }
/* eliminitate duplicated slashes */