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selftests/memfd: add tests for F_SEAL_FUTURE_WRITE seal
Add tests to verify sealing memfds with the F_SEAL_FUTURE_WRITE works as expected. Link: http://lkml.kernel.org/r/20190112203816.85534-3-joel@joelfernandes.org Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Reviewed-by: Shuah Khan <shuah@kernel.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andy Lutomirski <luto@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jann Horn <jannh@google.com> Cc: J. Bruce Fields <bfields@fieldses.org> Cc: Jeff Layton <jlayton@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Marc-Andr Lureau <marcandre.lureau@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -54,6 +54,22 @@ static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
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return fd;
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}
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static int mfd_assert_reopen_fd(int fd_in)
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{
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int r, fd;
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char path[100];
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sprintf(path, "/proc/self/fd/%d", fd_in);
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fd = open(path, O_RDWR);
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if (fd < 0) {
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printf("re-open of existing fd %d failed\n", fd_in);
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abort();
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}
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return fd;
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}
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static void mfd_fail_new(const char *name, unsigned int flags)
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{
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int r;
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@ -255,6 +271,25 @@ static void mfd_assert_read(int fd)
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munmap(p, mfd_def_size);
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}
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/* Test that PROT_READ + MAP_SHARED mappings work. */
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static void mfd_assert_read_shared(int fd)
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{
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void *p;
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/* verify PROT_READ and MAP_SHARED *is* allowed */
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p = mmap(NULL,
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mfd_def_size,
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PROT_READ,
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MAP_SHARED,
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fd,
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0);
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if (p == MAP_FAILED) {
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printf("mmap() failed: %m\n");
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abort();
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}
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munmap(p, mfd_def_size);
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}
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static void mfd_assert_write(int fd)
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{
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ssize_t l;
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@ -692,6 +727,44 @@ static void test_seal_write(void)
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close(fd);
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}
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/*
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* Test SEAL_FUTURE_WRITE
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* Test whether SEAL_FUTURE_WRITE actually prevents modifications.
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*/
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static void test_seal_future_write(void)
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{
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int fd, fd2;
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void *p;
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printf("%s SEAL-FUTURE-WRITE\n", memfd_str);
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fd = mfd_assert_new("kern_memfd_seal_future_write",
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mfd_def_size,
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MFD_CLOEXEC | MFD_ALLOW_SEALING);
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p = mfd_assert_mmap_shared(fd);
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mfd_assert_has_seals(fd, 0);
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mfd_assert_add_seals(fd, F_SEAL_FUTURE_WRITE);
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mfd_assert_has_seals(fd, F_SEAL_FUTURE_WRITE);
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/* read should pass, writes should fail */
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mfd_assert_read(fd);
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mfd_assert_read_shared(fd);
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mfd_fail_write(fd);
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fd2 = mfd_assert_reopen_fd(fd);
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/* read should pass, writes should still fail */
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mfd_assert_read(fd2);
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mfd_assert_read_shared(fd2);
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mfd_fail_write(fd2);
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munmap(p, mfd_def_size);
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close(fd2);
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close(fd);
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}
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/*
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* Test SEAL_SHRINK
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* Test whether SEAL_SHRINK actually prevents shrinking
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@ -945,6 +1018,7 @@ int main(int argc, char **argv)
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test_basic();
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test_seal_write();
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test_seal_future_write();
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test_seal_shrink();
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test_seal_grow();
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test_seal_resize();
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