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exec: provide right hardlink name in AT_EXECPATH

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For this, use vn_fullpath_hardlink() to resolve executable name for
execve(2).

This should provide the right hardlink name, used for execution, instead
of random hardlink pointing to this binary.  Also this should make the
AT_EXECNAME reliable for execve(2), since kernel only needs to resolve
parent directory path, which should always succeed (except pathological
cases like unlinking a directory).

PR:	248184
Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D32611
This commit is contained in:
Konstantin Belousov 2021-10-23 03:24:08 +03:00
parent 9a0bee9f6a
commit 0c10648fbb
1 changed files with 28 additions and 10 deletions
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38
sys/kern/kern_exec.c
View file

@ -432,6 +432,7 @@ do_execve(struct thread *td, struct image_args *args, struct mac *mac_p,
int error, i, orig_osrel;
uint32_t orig_fctl0;
Elf_Brandinfo *orig_brandinfo;
size_t freepath_size;
static const char fexecv_proc_title[] = "(fexecv)";
imgp = &image_params;
@ -479,7 +480,8 @@ do_execve(struct thread *td, struct image_args *args, struct mac *mac_p,
*/
if (args->fname != NULL) {
NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | LOCKSHARED | FOLLOW |
SAVENAME | AUDITVNODE1, UIO_SYSSPACE, args->fname, td);
SAVENAME | AUDITVNODE1 | WANTPARENT,
UIO_SYSSPACE, args->fname, td);
}
SDT_PROBE1(proc, , , exec, args->fname);
@ -625,9 +627,18 @@ interpret:
/*
* Do the best to calculate the full path to the image file.
*/
if (args->fname != NULL && args->fname[0] == '/')
imgp->execpath = args->fname;
else {
if (args->fname != NULL) {
if (args->fname[0] == '/') {
imgp->execpath = args->fname;
} else {
VOP_UNLOCK(imgp->vp);
freepath_size = MAXPATHLEN;
if (vn_fullpath_hardlink(&nd, &imgp->execpath,
&imgp->freepath, &freepath_size) != 0)
imgp->execpath = args->fname;
vn_lock(imgp->vp, LK_SHARED | LK_RETRY);
}
} else {
VOP_UNLOCK(imgp->vp);
if (vn_fullpath(imgp->vp, &imgp->execpath,
&imgp->freepath) != 0)
@ -680,8 +691,6 @@ interpret:
VOP_UNSET_TEXT_CHECKED(newtextvp);
imgp->textset = false;
/* free name buffer and old vnode */
if (args->fname != NULL)
NDFREE(&nd, NDF_ONLY_PNBUF);
#ifdef MAC
mac_execve_interpreter_enter(newtextvp, &interpvplabel);
#endif
@ -690,6 +699,11 @@ interpret:
imgp->opened = false;
}
vput(newtextvp);
if (args->fname != NULL) {
if (nd.ni_dvp != NULL)
vrele(nd.ni_dvp);
NDFREE(&nd, NDF_ONLY_PNBUF);
}
vm_object_deallocate(imgp->object);
imgp->object = NULL;
execve_nosetid(imgp);
@ -697,9 +711,10 @@ interpret:
free(imgp->freepath, M_TEMP);
imgp->freepath = NULL;
/* set new name to that of the interpreter */
NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | LOCKSHARED | FOLLOW |
SAVENAME, UIO_SYSSPACE, imgp->interpreter_name, td);
args->fname = imgp->interpreter_name;
NDINIT(&nd, LOOKUP, ISOPEN | LOCKLEAF | LOCKSHARED | FOLLOW |
SAVENAME | WANTPARENT,
UIO_SYSSPACE, imgp->interpreter_name, td);
goto interpret;
}
@ -930,8 +945,6 @@ exec_fail_dealloc:
exec_unmap_first_page(imgp);
if (imgp->vp != NULL) {
if (args->fname)
NDFREE(&nd, NDF_ONLY_PNBUF);
if (imgp->opened)
VOP_CLOSE(imgp->vp, FREAD, td->td_ucred, td);
if (imgp->textset)
@ -940,6 +953,11 @@ exec_fail_dealloc:
vput(imgp->vp);
else
VOP_UNLOCK(imgp->vp);
if (args->fname != NULL) {
if (nd.ni_dvp != NULL)
vrele(nd.ni_dvp);
NDFREE(&nd, NDF_ONLY_PNBUF);
}
}
if (imgp->object != NULL)