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author | Eric W. Biederman <ebiederm@xmission.com> | 2020-04-04 09:42:56 -0500 |
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committer | Eric W. Biederman <ebiederm@xmission.com> | 2020-05-11 12:08:49 -0500 |
commit | 8890b29341f30f4a364b2eb6046bb1ac1478f955 (patch) | |
tree | 69e5fa0629458b55ef3dd929310421729cc56322 /fs/exec.c | |
parent | a28bf136e651e17d7e2c753aa140ce3cc1df36a0 (diff) | |
download | linux-8890b29341f30f4a364b2eb6046bb1ac1478f955.tar.gz linux-8890b29341f30f4a364b2eb6046bb1ac1478f955.tar.bz2 linux-8890b29341f30f4a364b2eb6046bb1ac1478f955.zip |
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.c | 21 |
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); |