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authorEric W. Biederman <ebiederm@xmission.com>2020-07-10 15:54:54 -0500
committerEric W. Biederman <ebiederm@xmission.com>2020-07-21 08:24:52 -0500
commitf18ac551e5035a52fd8edadc45e0f8eb4cec8d3e (patch)
tree47df741fabcbebc556fc8e9f28b466e9938eea38 /fs/exec.c
parent60d9ad1d1d7f15964d23f6e71a7adcf1bde0e18e (diff)
downloadlinux-f18ac551e5035a52fd8edadc45e0f8eb4cec8d3e.tar.bz2
exec: Move bprm_mm_init into alloc_bprm
Currently it is necessary for the usermode helper code and the code that launches init to use set_fs so that pages coming from the kernel look like they are coming from userspace. To allow that usage of set_fs to be removed cleanly the argument copying from userspace needs to happen earlier. Move the allocation and initialization of bprm->mm into alloc_bprm so that the bprm->mm is available early to store the new user stack into. This is a prerequisite for copying argv and envp into the new user stack early before ther rest of exec. To keep the things consistent the cleanup of bprm->mm is moved into free_bprm. So that bprm->mm will be cleaned up whenever bprm->mm is allocated and free_bprm are called. Moving bprm_mm_init earlier is safe as it does not depend on any files, current->in_execve, current->fs->in_exec, bprm->unsafe, or the if the file table is shared. (AKA bprm_mm_init does not depend on any of the code that happens between alloc_bprm and where it was previously called.) This moves bprm->mm cleanup after current->fs->in_exec is set to 0. This is safe because current->fs->in_exec is only used to preventy taking an additional reference on the fs_struct. This moves bprm->mm cleanup after current->in_execve is set to 0. This is safe because current->in_execve is only used by the lsms (apparmor and tomoyou) and always for LSM specific functions, never for anything to do with the mm. This adds bprm->mm cleanup into the successful return path. This is safe because being on the successful return path implies that begin_new_exec succeeded and set brpm->mm to NULL. As bprm->mm is NULL bprm cleanup I am moving into free_bprm will do nothing. Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lkml.kernel.org/r/87eepe6x7p.fsf@x220.int.ebiederm.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 7e8af27dd199..afb168bf5e23 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1543,6 +1543,10 @@ static int prepare_bprm_creds(struct linux_binprm *bprm)
static void free_bprm(struct linux_binprm *bprm)
{
+ if (bprm->mm) {
+ acct_arg_size(bprm, 0);
+ mmput(bprm->mm);
+ }
free_arg_pages(bprm);
if (bprm->cred) {
mutex_unlock(&current->signal->cred_guard_mutex);
@@ -1582,6 +1586,10 @@ static struct linux_binprm *alloc_bprm(int fd, struct filename *filename)
bprm->filename = bprm->fdpath;
}
bprm->interp = bprm->filename;
+
+ retval = bprm_mm_init(bprm);
+ if (retval)
+ goto out_free;
return bprm;
out_free:
@@ -1911,10 +1919,6 @@ static int do_execveat_common(int fd, struct filename *filename,
close_on_exec(fd, rcu_dereference_raw(current->files->fdt)))
bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
- retval = bprm_mm_init(bprm);
- if (retval)
- goto out_unmark;
-
retval = prepare_arg_pages(bprm, argv, envp);
if (retval < 0)
goto out;
@@ -1962,10 +1966,6 @@ out:
*/
if (bprm->point_of_no_return && !fatal_signal_pending(current))
force_sigsegv(SIGSEGV);
- if (bprm->mm) {
- acct_arg_size(bprm, 0);
- mmput(bprm->mm);
- }
out_unmark:
current->fs->in_exec = 0;