From: Oleg Nesterov <oleg@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Woodard <woodard@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Kees Cook <keescook@chromium.org>, Michal Hocko <mhocko@suse.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] exec: load_script: don't blindly truncate shebang string
Date: Mon, 12 Nov 2018 17:09:31 +0100 [thread overview]
Message-ID: <20181112160931.GA28463@redhat.com> (raw)
load_script() simply truncates bprm->buf and this is very wrong if the
length of shebang string exceeds BINPRM_BUF_SIZE-2. This can silently
truncate i_arg or (worse) we can execute the wrong binary if buf[2:126]
happens to be the valid executable path.
Change load_script() to return ENOEXEC if it can't find '\n' or zero in
bprm->buf. Note that '\0' can come from either prepare_binprm()->memset()
or from kernel_read(), we do not care.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
fs/binfmt_script.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c
index 7cde3f4..d0078cb 100644
--- a/fs/binfmt_script.c
+++ b/fs/binfmt_script.c
@@ -42,10 +42,14 @@ static int load_script(struct linux_binprm *bprm)
fput(bprm->file);
bprm->file = NULL;
- bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';
- if ((cp = strchr(bprm->buf, '\n')) == NULL)
- cp = bprm->buf+BINPRM_BUF_SIZE-1;
+ for (cp = bprm->buf+2;; cp++) {
+ if (cp >= bprm->buf + BINPRM_BUF_SIZE)
+ return -ENOEXEC;
+ if (!*cp || (*cp == '\n'))
+ break;
+ }
*cp = '\0';
+
while (cp > bprm->buf) {
cp--;
if ((*cp == ' ') || (*cp == '\t'))
--
2.5.0
next reply other threads:[~2018-11-12 16:09 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-12 16:09 Oleg Nesterov [this message]
2018-11-12 16:09 ` [PATCH 2/2] exec: increase BINPRM_BUF_SIZE to 256 Oleg Nesterov
2018-11-12 23:52 ` Andrew Morton
2018-11-13 5:03 ` Kees Cook
2018-11-13 16:55 ` Oleg Nesterov
2018-11-13 20:43 ` Andrew Morton
2018-11-14 15:54 ` Oleg Nesterov
2018-11-14 16:01 ` Michal Hocko
2018-11-13 10:29 ` Michal Hocko
2018-11-16 17:49 ` Alan Cox
2018-11-22 12:15 ` Oleg Nesterov
[not found] ` <20181121160753.GA32685@asgard.redhat.com>
[not found] ` <CAKgNAkhFikJXeOx3W3yL3EUKa9ruXtAw93m4M=N+3Kg-bXbPDQ@mail.gmail.com>
2018-11-22 17:32 ` [PATCH] execve.2: document an effect of BINPRM_BUF_SIZE increase " Eugene Syromiatnikov
2019-02-18 19:37 ` [PATCH 2/2] exec: increase BINPRM_BUF_SIZE " Guenter Roeck
2019-02-19 12:37 ` Oleg Nesterov
2019-02-19 16:26 ` Guenter Roeck
2019-02-19 17:36 ` Oleg Nesterov
2018-11-13 10:27 ` [PATCH 1/2] exec: load_script: don't blindly truncate shebang string Michal Hocko
2018-11-13 16:41 ` Oleg Nesterov
2018-11-13 20:16 ` Kees Cook
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