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d8238f9eb6
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
79 lines
1.8 KiB
C
79 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define _GNU_SOURCE
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#include <sched.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <signal.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <sys/ioctl.h>
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#include <sys/prctl.h>
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#include <sys/wait.h>
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#define pr_err(fmt, ...) \
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({ \
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fprintf(stderr, "%s:%d:" fmt ": %m\n", \
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__func__, __LINE__, ##__VA_ARGS__); \
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1; \
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})
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#define NSIO 0xb7
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#define NS_GET_USERNS _IO(NSIO, 0x1)
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#define NS_GET_PARENT _IO(NSIO, 0x2)
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#define __stack_aligned__ __attribute__((aligned(16)))
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struct cr_clone_arg {
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char stack[128] __stack_aligned__;
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char stack_ptr[];
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};
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static int child(void *args)
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{
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prctl(PR_SET_PDEATHSIG, SIGKILL);
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while (1)
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sleep(1);
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exit(0);
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}
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int main(int argc, char *argv[])
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{
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char *ns_strs[] = {"pid", "user"};
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char path[] = "/proc/0123456789/ns/pid";
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struct cr_clone_arg ca;
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struct stat st1, st2;
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int ns, pns, i;
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pid_t pid;
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pid = clone(child, ca.stack_ptr, CLONE_NEWUSER | CLONE_NEWPID | SIGCHLD, NULL);
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if (pid < 0)
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return pr_err("clone");
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for (i = 0; i < 2; i++) {
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snprintf(path, sizeof(path), "/proc/%d/ns/%s", pid, ns_strs[i]);
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ns = open(path, O_RDONLY);
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if (ns < 0)
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return pr_err("Unable to open %s", path);
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pns = ioctl(ns, NS_GET_PARENT);
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if (pns < 0)
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return pr_err("Unable to get a parent pidns");
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snprintf(path, sizeof(path), "/proc/self/ns/%s", ns_strs[i]);
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if (stat(path, &st2))
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return pr_err("Unable to stat %s", path);
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if (fstat(pns, &st1))
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return pr_err("Unable to stat the parent pidns");
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if (st1.st_ino != st2.st_ino)
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return pr_err("NS_GET_PARENT returned a wrong namespace");
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if (ioctl(pns, NS_GET_PARENT) >= 0 || errno != EPERM)
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return pr_err("Don't get EPERM");
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}
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kill(pid, SIGKILL);
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wait(NULL);
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return 0;
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}
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