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authorEric W. Biederman <ebiederm@xmission.com>2020-04-04 09:42:56 -0500
committerEric W. Biederman <ebiederm@xmission.com>2020-05-11 12:08:49 -0500
commit8890b29341f30f4a364b2eb6046bb1ac1478f955 (patch)
tree69e5fa0629458b55ef3dd929310421729cc56322 /fs/exec.c
parenta28bf136e651e17d7e2c753aa140ce3cc1df36a0 (diff)
downloadlinux-8890b29341f30f4a364b2eb6046bb1ac1478f955.tar.bz2
exec: Move handling of the point of no return to the top level
Move the handing of the point of no return from search_binary_handler into __do_execve_file so that it is easier to find, and to keep things robust in the face of change. Make it clear that an existing fatal signal will take precedence over a forced SIGSEGV by not forcing SIGSEGV if a fatal signal is already pending. This does not change the behavior but it saves a reader of the code the tedium of reading and understanding force_sig and the signal delivery code. Update the comment in begin_new_exec about where SIGSEGV is forced. Keep point_of_no_return from being a mystery by documenting what the code is doing where it forces SIGSEGV if the code is past the point of no return. Reviewed-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/87y2q25knl.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.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/fs/exec.c b/fs/exec.c
index ecee0ebebf85..fa265ea322b7 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1329,8 +1329,8 @@ int begin_new_exec(struct linux_binprm * bprm)
/*
* With the new mm installed it is completely impossible to
* fail and return to the original process. If anything from
- * here on returns an error, the check in
- * search_binary_handler() will SEGV current.
+ * here on returns an error, the check in __do_execve_file()
+ * will SEGV current.
*/
bprm->point_of_no_return = true;
bprm->mm = NULL;
@@ -1721,13 +1721,8 @@ int search_binary_handler(struct linux_binprm *bprm)
read_lock(&binfmt_lock);
put_binfmt(fmt);
- if (retval < 0 && bprm->point_of_no_return) {
- /* we got to flush_old_exec() and failed after it */
- read_unlock(&binfmt_lock);
- force_sigsegv(SIGSEGV);
- return retval;
- }
- if (retval != -ENOEXEC || !bprm->file) {
+ if (bprm->point_of_no_return || !bprm->file ||
+ (retval != -ENOEXEC)) {
read_unlock(&binfmt_lock);
return retval;
}
@@ -1898,6 +1893,14 @@ static int __do_execve_file(int fd, struct filename *filename,
return retval;
out:
+ /*
+ * If past the point of no return ensure the the code never
+ * returns to the userspace process. Use an existing fatal
+ * signal if present otherwise terminate the process with
+ * SIGSEGV.
+ */
+ if (bprm->point_of_no_return && !fatal_signal_pending(current))
+ force_sigsegv(SIGSEGV);
if (bprm->mm) {
acct_arg_size(bprm, 0);
mmput(bprm->mm);