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authorOleg Nesterov <oleg@redhat.com>2019-01-03 23:28:07 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 21:13:47 (GMT)
commit8099b047ecc431518b9bb6bdbba3549bbecdc343 (patch)
treef0abafbb5f20984f92165e4da26fb37377dd497a /fs
parentfb5bf31722d0805a3f394f7d59f2e8cd07acccb7 (diff)
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@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>
Diffstat (limited to 'fs')
-rw-r--r--fs/binfmt_script.c10
1 files 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'))

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