Allow recursion in binfmt_script and binfmt_misc
binfmt_script and binfmt_misc disallow recursion to avoid stack overflow
using sh_bang and misc_bang. It causes problem in some cases:
$ echo '#!/bin/ls' > /tmp/t0
$ echo '#!/tmp/t0' > /tmp/t1
$ echo '#!/tmp/t1' > /tmp/t2
$ chmod +x /tmp/t*
$ /tmp/t2
zsh: exec format error: /tmp/t2
Similar problem with binfmt_misc.
This patch introduces field 'recursion_depth' into struct linux_binprm to
track recursion level in binfmt_misc and binfmt_script. If recursion
level more then BINPRM_MAX_RECURSION it generates -ENOEXEC.
[akpm@linux-foundation.org: make linux_binprm.recursion_depth a uint]
Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 8d7e88e..f2744ab 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -117,7 +117,7 @@
goto _ret;
retval = -ENOEXEC;
- if (bprm->misc_bang)
+ if (bprm->recursion_depth > BINPRM_MAX_RECURSION)
goto _ret;
/* to keep locking time low, we copy the interpreter string */
@@ -197,7 +197,7 @@
if (retval < 0)
goto _error;
- bprm->misc_bang = 1;
+ bprm->recursion_depth++;
retval = search_binary_handler (bprm, regs);
if (retval < 0)