[PATCH] exec: refactor an invalid executable check to use isprint

[PATCH] exec: refactor an invalid executable check to use isprint

[Nir Lichtman]

Remove private printable macro that is defined in exec.c and migrate to
using the public isprint macro instead

Signed-off-by: Nir Lichtman <nir@lichtman.org>
---
 fs/exec.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 6c53920795c2..3394de5882af 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1723,7 +1723,6 @@ int remove_arg_zero(struct linux_binprm *bprm)
 }
 EXPORT_SYMBOL(remove_arg_zero);
 
-#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
 /*
  * cycle the list of binary formats handler, until one recognizes the image
  */
@@ -1761,8 +1760,8 @@ static int search_binary_handler(struct linux_binprm *bprm)
 	read_unlock(&binfmt_lock);
 
 	if (need_retry) {
-		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
-		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
+		if (isprint(bprm->buf[0]) && isprint(bprm->buf[1]) &&
+		    isprint(bprm->buf[2]) && isprint(bprm->buf[3]))
 			return retval;
 		if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
 			return retval;
-- 
2.39.2

Re: [PATCH] exec: refactor an invalid executable check to use isprint

[Al Viro]

On Fri, Nov 15, 2024 at 04:53:51PM +0000, Nir Lichtman wrote:
> Remove private printable macro that is defined in exec.c and migrate to
> using the public isprint macro instead


> -#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))

> -		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
> -		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
> +		if (isprint(bprm->buf[0]) && isprint(bprm->buf[1]) &&
> +		    isprint(bprm->buf[2]) && isprint(bprm->buf[3]))

RTFM(isprint).  Or run a trivial loop and check what it does, for that
matter.

isprint('\t') is false.  So's isprint('\n').

Re: [PATCH] exec: refactor an invalid executable check to use isprint

[Nir Lichtman]

On Fri, Nov 15, 2024 at 05:04:47PM +0000, Al Viro wrote:
> On Fri, Nov 15, 2024 at 04:53:51PM +0000, Nir Lichtman wrote:
> > Remove private printable macro that is defined in exec.c and migrate to
> > using the public isprint macro instead
> 
> 
> > -#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
> 
> > -		if (printable(bprm->buf[0]) && printable(bprm->buf[1]) &&
> > -		    printable(bprm->buf[2]) && printable(bprm->buf[3]))
> > +		if (isprint(bprm->buf[0]) && isprint(bprm->buf[1]) &&
> > +		    isprint(bprm->buf[2]) && isprint(bprm->buf[3]))
> 
> RTFM(isprint).  Or run a trivial loop and check what it does, for that
> matter.
> 
> isprint('\t') is false.  So's isprint('\n').

Right my bad I read _SP as _S by mistake, I'll send out another version with a fix considering the spaces