The patch titled
Subject: exec: load_script: don't blindly truncate shebang string
has been added to the -mm tree. Its filename is
exec-load_script-dont-blindly-truncate-shebang-string.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/exec-load_script-dont-blindly-truncate-shebang-string.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/exec-load_script-dont-blindly-truncate-shebang-string.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: exec: load_script: don't blindly truncate shebang string
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@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Ben Woodard <woodard@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_script.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
--- a/fs/binfmt_script.c~exec-load_script-dont-blindly-truncate-shebang-string
+++ a/fs/binfmt_script.c
@@ -42,10 +42,14 @@ static int load_script(struct linux_binp
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'))
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
exec-load_script-dont-blindly-truncate-shebang-string.patch
exec-increase-binprm_buf_size-to-256.patch
