From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Oleg Nesterov <oleg@redhat.com>, Ben Woodard <woodard@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sasha Levin <sashal@kernel.org>,
linux-fsdevel@vger.kernel.org
Subject: [PATCH AUTOSEL 4.9 107/107] exec: load_script: don't blindly truncate shebang string
Date: Mon, 28 Jan 2019 11:19:47 -0500 [thread overview]
Message-ID: <20190128161947.57405-107-sashal@kernel.org> (raw)
In-Reply-To: <20190128161947.57405-1-sashal@kernel.org>
From: Oleg Nesterov <oleg@redhat.com>
[ Upstream commit 8099b047ecc431518b9bb6bdbba3549bbecdc343 ]
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.
Link: http://lkml.kernel.org/r/20181112160931.GA28463@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ben Woodard <woodard@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 afdf4e3cafc2..634bdbb23851 100644
--- a/fs/binfmt_script.c
+++ b/fs/binfmt_script.c
@@ -43,10 +43,14 @@ 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'))
--
2.19.1
prev parent reply other threads:[~2019-01-28 16:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190128161947.57405-1-sashal@kernel.org>
2019-01-28 16:19 ` [PATCH AUTOSEL 4.9 103/107] fs/proc/base.c: use ns_capable instead of capable for timerslack_ns Sasha Levin
2019-01-28 16:19 ` [PATCH AUTOSEL 4.9 105/107] proc/sysctl: fix return error for proc_doulongvec_minmax() Sasha Levin
2019-01-28 16:19 ` [PATCH AUTOSEL 4.9 106/107] fs/epoll: drop ovflist branch prediction Sasha Levin
2019-01-28 16:19 ` Sasha Levin [this message]
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