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exec: Add do_close_execat() helper

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Consolidate the calls to allow_write_access()/fput() into a single
place, since we repeat this code pattern. Add comments around the
callers for the details on it.

Link: https://lore.kernel.org/r/202209161637.9EDAF6B18@keescook
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2022-09-16 17:11:18 -07:00
parent 8788a17c23
commit bdd8f62431
1 changed files with 26 additions and 6 deletions
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32
fs/exec.c
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@ -904,6 +904,10 @@ EXPORT_SYMBOL(transfer_args_to_stack);
#endif /* CONFIG_MMU */
/*
* On success, caller must call do_close_execat() on the returned
* struct file to close it.
*/
static struct file *do_open_execat(int fd, struct filename *name, int flags)
{
struct file *file;
@ -948,6 +952,17 @@ static struct file *do_open_execat(int fd, struct filename *name, int flags)
return ERR_PTR(err);
}
/**
* open_exec - Open a path name for execution
*
* @name: path name to open with the intent of executing it.
*
* Returns ERR_PTR on failure or allocated struct file on success.
*
* As this is a wrapper for the internal do_open_execat(), callers
* must call allow_write_access() before fput() on release. Also see
* do_close_execat().
*/
struct file *open_exec(const char *name)
{
struct filename *filename = getname_kernel(name);
@ -1484,6 +1499,15 @@ static int prepare_bprm_creds(struct linux_binprm *bprm)
return -ENOMEM;
}
/* Matches do_open_execat() */
static void do_close_execat(struct file *file)
{
if (!file)
return;
allow_write_access(file);
fput(file);
}
static void free_bprm(struct linux_binprm *bprm)
{
if (bprm->mm) {
@ -1495,10 +1519,7 @@ static void free_bprm(struct linux_binprm *bprm)
mutex_unlock(&current->signal->cred_guard_mutex);
abort_creds(bprm->cred);
}
if (bprm->file) {
allow_write_access(bprm->file);
fput(bprm->file);
}
do_close_execat(bprm->file);
if (bprm->executable)
fput(bprm->executable);
/* If a binfmt changed the interp, free it. */
@ -1520,8 +1541,7 @@ static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int fl
bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
if (!bprm) {
allow_write_access(file);
fput(file);
do_close_execat(file);
return ERR_PTR(-ENOMEM);
}