The patch titled
Allow recursion in binfmt_script and binfmt_misc
has been added to the -mm tree. Its filename is
allow-recursion-in-binfmt_script-and-binfmt_misc.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: Allow recursion in binfmt_script and binfmt_misc
From: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
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.
Signed-off-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_em86.c | 2 +-
fs/binfmt_misc.c | 4 ++--
fs/binfmt_script.c | 5 +++--
include/linux/binfmts.h | 2 ++
4 files changed, 8 insertions(+), 5 deletions(-)
diff -puN fs/binfmt_em86.c~allow-recursion-in-binfmt_script-and-binfmt_misc fs/binfmt_em86.c
--- a/fs/binfmt_em86.c~allow-recursion-in-binfmt_script-and-binfmt_misc
+++ a/fs/binfmt_em86.c
@@ -43,7 +43,7 @@ static int load_em86(struct linux_binprm
return -ENOEXEC;
}
- bprm->sh_bang = 1; /* Well, the bang-shell is implicit... */
+ bprm->recursion_depth++; /* Well, the bang-shell is implicit... */
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
diff -puN fs/binfmt_misc.c~allow-recursion-in-binfmt_script-and-binfmt_misc fs/binfmt_misc.c
--- a/fs/binfmt_misc.c~allow-recursion-in-binfmt_script-and-binfmt_misc
+++ a/fs/binfmt_misc.c
@@ -117,7 +117,7 @@ static int load_misc_binary(struct linux
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 @@ static int load_misc_binary(struct linux
if (retval < 0)
goto _error;
- bprm->misc_bang = 1;
+ bprm->recursion_depth++;
retval = search_binary_handler (bprm, regs);
if (retval < 0)
diff -puN fs/binfmt_script.c~allow-recursion-in-binfmt_script-and-binfmt_misc fs/binfmt_script.c
--- a/fs/binfmt_script.c~allow-recursion-in-binfmt_script-and-binfmt_misc
+++ a/fs/binfmt_script.c
@@ -22,14 +22,15 @@ static int load_script(struct linux_binp
char interp[BINPRM_BUF_SIZE];
int retval;
- if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!') || (bprm->sh_bang))
+ if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!') ||
+ (bprm->recursion_depth > BINPRM_MAX_RECURSION))
return -ENOEXEC;
/*
* This section does the #! interpretation.
* Sorta complicated, but hopefully it will work. -TYT
*/
- bprm->sh_bang = 1;
+ bprm->recursion_depth++;
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
diff -puN include/linux/binfmts.h~allow-recursion-in-binfmt_script-and-binfmt_misc include/linux/binfmts.h
--- a/include/linux/binfmts.h~allow-recursion-in-binfmt_script-and-binfmt_misc
+++ a/include/linux/binfmts.h
@@ -44,6 +44,7 @@ struct linux_binprm{
#ifdef __alpha__
unsigned int taso:1;
#endif
+ unsigned char recursion_depth;
struct file * file;
struct cred *cred; /* new credentials */
int unsafe; /* how unsafe this exec is (mask of LSM_UNSAFE_*) */
@@ -65,6 +66,7 @@ struct linux_binprm{
#define BINPRM_FLAGS_EXECFD_BIT 1
#define BINPRM_FLAGS_EXECFD (1 << BINPRM_FLAGS_EXECFD_BIT)
+#define BINPRM_MAX_RECURSION 4
/*
* This structure defines the functions that are used to load the binary formats that
_
Patches currently in -mm which might be from kirill@xxxxxxxxxxxxx are
alpha-introduce-field-taso-into-struct-linux_binprm.patch
allow-recursion-in-binfmt_script-and-binfmt_misc.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
