[PATCH] generic/633: pass non-empty argv with execveat()
From: Christian Brauner
Date: Wed Feb 02 2022 - 04:52:25 EST
So far the kernel allowed passing an empty argv. Given that there's now
a push to restrict the kernel in that regard make sure we pass at least
one argument with argv.
Cc: Ariadne Conill <ariadne@xxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Rich Felker <dalias@xxxxxxxx>
Cc: Eryu Guan <guaneryu@xxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: fstests@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/lkml/20220127000724.15106-1-ariadne@xxxxxxxxxxxxxxxx
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
/* v2 */
- Make sure argv array is NULL terminated. I fired the first patch too
quickly.
- Take the chance and remove the repeated argv open-coding and move it
directly into the execveat helper and rename it to reflect the fact
that it's not just a simple syscall wrapper anymore.
---
src/idmapped-mounts/idmapped-mounts.c | 65 +++++++++------------------
1 file changed, 22 insertions(+), 43 deletions(-)
diff --git a/src/idmapped-mounts/idmapped-mounts.c b/src/idmapped-mounts/idmapped-mounts.c
index 4cf6c3bb..5bab19a9 100644
--- a/src/idmapped-mounts/idmapped-mounts.c
+++ b/src/idmapped-mounts/idmapped-mounts.c
@@ -695,11 +695,14 @@ static int fd_to_fd(int from, int to)
return 0;
}
-static int sys_execveat(int fd, const char *path, char **argv, char **envp,
- int flags)
+static int do_execveat(int fd, const char *path, char **envp)
{
#ifdef __NR_execveat
- return syscall(__NR_execveat, fd, path, argv, envp, flags);
+ static char *argv_empty[] = {
+ "",
+ NULL,
+ };
+ return syscall(__NR_execveat, fd, path, argv_empty, envp, 0);
#else
errno = ENOSYS;
return -1;
@@ -3597,15 +3600,12 @@ static int setid_binaries(void)
"EXPECTED_EGID=5000",
NULL,
};
- static char *argv[] = {
- NULL,
- };
if (!expected_uid_gid(t_dir1_fd, FILE1, 0, 5000, 5000))
die("failure: expected_uid_gid");
- sys_execveat(t_dir1_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(t_dir1_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -3725,15 +3725,12 @@ static int setid_binaries_idmapped_mounts(void)
"EXPECTED_EGID=15000",
NULL,
};
- static char *argv[] = {
- NULL,
- };
if (!expected_uid_gid(open_tree_fd, FILE1, 0, 15000, 15000))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -3864,9 +3861,6 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
"EXPECTED_EGID=5000",
NULL,
};
- static char *argv[] = {
- NULL,
- };
if (!switch_userns(attr.userns_fd, 0, 0, false))
die("failure: switch_userns");
@@ -3874,8 +3868,8 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
if (!expected_uid_gid(open_tree_fd, FILE1, 0, 5000, 5000))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -3923,9 +3917,6 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
"EXPECTED_EGID=0",
NULL,
};
- static char *argv[] = {
- NULL,
- };
if (!caps_supported()) {
log_debug("skip: capability library not installed");
@@ -3938,8 +3929,8 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 0))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -3991,9 +3982,6 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
NULL,
NULL,
};
- static char *argv[] = {
- NULL,
- };
if (!switch_userns(attr.userns_fd, 0, 0, false))
die("failure: switch_userns");
@@ -4007,8 +3995,8 @@ static int setid_binaries_idmapped_mounts_in_userns(void)
if (!expected_uid_gid(open_tree_fd, FILE1, 0, t_overflowuid, t_overflowgid))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -4149,9 +4137,6 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
"EXPECTED_EGID=5000",
NULL,
};
- static char *argv[] = {
- NULL,
- };
userns_fd = get_userns_fd(0, 10000, 10000);
if (userns_fd < 0)
@@ -4163,8 +4148,8 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
if (!expected_uid_gid(open_tree_fd, FILE1, 0, 5000, 5000))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -4213,9 +4198,6 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
"EXPECTED_EGID=0",
NULL,
};
- static char *argv[] = {
- NULL,
- };
userns_fd = get_userns_fd(0, 10000, 10000);
if (userns_fd < 0)
@@ -4232,8 +4214,8 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 0))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
@@ -4285,9 +4267,6 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
NULL,
NULL,
};
- static char *argv[] = {
- NULL,
- };
userns_fd = get_userns_fd(0, 10000, 10000);
if (userns_fd < 0)
@@ -4305,8 +4284,8 @@ static int setid_binaries_idmapped_mounts_in_userns_separate_userns(void)
if (!expected_uid_gid(open_tree_fd, FILE1, 0, t_overflowuid, t_overflowgid))
die("failure: expected_uid_gid");
- sys_execveat(open_tree_fd, FILE1, argv, envp, 0);
- die("failure: sys_execveat");
+ do_execveat(open_tree_fd, FILE1, envp);
+ die("failure: do_execveat");
exit(EXIT_FAILURE);
}
base-commit: d8dee1222ecdfa1cff1386a61248e587eb3b275d
--
2.32.0