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exec: load_script: don't blindly truncate shebang string

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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/[email protected]
Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Kees Cook <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Ben Woodard <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Oleg Nesterov
2019-01-04 13:13:47 -08:00
committed by Linus Torvalds
parent fb5bf31722
commit 8099b047ec
1 changed files with 7 additions and 3 deletions
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fs/binfmt_script.c
+7 -3
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@@ -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'))