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exec: remove legacy custom binfmt modules autoloading

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Problem: The search binary handler logic contains legacy code
to handle automatically loading kernel modules of unsupported
binary formats.
This logic is a leftover from a.out-to-ELF transition.
After removal of a.out support, this code has no use anymore.

Solution: Clean up this code from the search binary handler,
also remove the line initialising retval to -ENOENT and instead
just return -ENOEXEC if the flow has reached the end of the func.

Note: Anyone who might find future uses for this legacy code
would be better off using binfmt_misc to trigger whatever
module loading they might need - would be more flexible that way.

Suggested-by: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Nir Lichtman <nir@lichtman.org>
Link: https://lore.kernel.org/r/20241116231323.GA225987@lichtman.org
Signed-off-by: Kees Cook <kees@kernel.org>
This commit is contained in:
Nir Lichtman 2024-11-16 23:13:23 +00:00 committed by Kees Cook
parent 4188fc31a9
commit fa1bdca98d
1 changed files with 1 additions and 15 deletions
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16
fs/exec.c
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@ -1723,13 +1723,11 @@ 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
*/
static int search_binary_handler(struct linux_binprm *bprm)
{
bool need_retry = IS_ENABLED(CONFIG_MODULES);
struct linux_binfmt *fmt;
int retval;
@ -1741,8 +1739,6 @@ static int search_binary_handler(struct linux_binprm *bprm)
if (retval)
return retval;
retval = -ENOENT;
retry:
read_lock(&binfmt_lock);
list_for_each_entry(fmt, &formats, lh) {
if (!try_module_get(fmt->module))
@ -1760,17 +1756,7 @@ 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]))
return retval;
if (request_module("binfmt-%04x", *(ushort *)(bprm->buf + 2)) < 0)
return retval;
need_retry = false;
goto retry;
}
return retval;
return -ENOEXEC;
}
/* binfmt handlers will call back into begin_new_exec() on success. */