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authorEric W. Biederman <ebiederm@xmission.com>2020-05-14 15:17:40 -0500
committerEric W. Biederman <ebiederm@xmission.com>2020-05-21 10:16:57 -0500
commitb8a61c9e7b4a0fec493d191429e9653d66a79ccc (patch)
tree91d7cfb679da13a3f096cbe8d7cd9d340afd2832 /fs/exec.c
parentccbb18b67323b5c70b5f07177381d14cd002621f (diff)
exec: Generic execfd support
Most of the support for passing the file descriptor of an executable to an interpreter already lives in the generic code and in binfmt_elf. Rework the fields in binfmt_elf that deal with executable file descriptor passing to make executable file descriptor passing a first class concept. Move the fd_install from binfmt_misc into begin_new_exec after the new creds have been installed. This means that accessing the file through /proc/<pid>/fd/N is able to see the creds for the new executable before allowing access to the new executables files. Performing the install of the executables file descriptor after the point of no return also means that nothing special needs to be done on error. The exiting of the process will close all of it's open files. Move the would_dump from binfmt_misc into begin_new_exec right after would_dump is called on the bprm->file. This makes it obvious this case exists and that no nesting of bprm->file is currently supported. In binfmt_misc the movement of fd_install into generic code means that it's special error exit path is no longer needed. Link: https://lkml.kernel.org/r/87y2poyd91.fsf_-_@x220.int.ebiederm.org Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 5fc458460e44..117ad8fc012b 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1323,7 +1323,10 @@ int begin_new_exec(struct linux_binprm * bprm)
*/
set_mm_exe_file(bprm->mm, bprm->file);
+ /* If the binary is not readable then enforce mm->dumpable=0 */
would_dump(bprm, bprm->file);
+ if (bprm->have_execfd)
+ would_dump(bprm, bprm->executable);
/*
* Release all of the old mmap stuff
@@ -1427,6 +1430,16 @@ int begin_new_exec(struct linux_binprm * bprm)
* credentials; any time after this it may be unlocked.
*/
security_bprm_committed_creds(bprm);
+
+ /* Pass the opened binary to the interpreter. */
+ if (bprm->have_execfd) {
+ retval = get_unused_fd_flags(0);
+ if (retval < 0)
+ goto out_unlock;
+ fd_install(retval, bprm->executable);
+ bprm->executable = NULL;
+ bprm->execfd = retval;
+ }
return 0;
out_unlock:
@@ -1516,6 +1529,8 @@ static void free_bprm(struct linux_binprm *bprm)
allow_write_access(bprm->file);
fput(bprm->file);
}
+ if (bprm->executable)
+ fput(bprm->executable);
/* If a binfmt changed the interp, free it. */
if (bprm->interp != bprm->filename)
kfree(bprm->interp);