From: Dave Hansen dave.hansen@linux.intel.com
mainline inclusion from mainline-v5.13-rc1 commit 4284f7acb78bfb0e0c26a2b78e2b2c3d68fccd6f category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I4SIGI CVE: NA
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The SGX device file (/dev/sgx_enclave) is unusual in that it requires execute permissions. It has to be both "chmod +x" *and* be on a filesystem without 'noexec'.
In the future, udev and systemd should get updates to set up systems automatically. But, for now, nobody's systems do this automatically, and everybody gets error messages like this when running ./test_sgx:
0x0000000000000000 0x0000000000002000 0x03 0x0000000000002000 0x0000000000001000 0x05 0x0000000000003000 0x0000000000003000 0x03 mmap() failed, errno=1.
That isn't very user friendly, even for forgetful kernel developers.
Further, the test case is rather haphazard about its use of fprintf() versus perror().
Improve the error messages. Use perror() where possible. Lastly, do some sanity checks on opening and mmap()ing the device file so that we can get a decent error message out to the user.
Now, if your user doesn't have permission, you'll get the following:
$ ls -l /dev/sgx_enclave [ Fan Du: amend commit log ] Signed-off-by: Fan Du fan.du@intel.com crw------- 1 root root 10, 126 Mar 18 11:29 /dev/sgx_enclave $ ./test_sgx Unable to open /dev/sgx_enclave: Permission denied
If you then 'chown dave:dave /dev/sgx_enclave' (or whatever), but you leave execute permissions off, you'll get:
$ ls -l /dev/sgx_enclave crw------- 1 dave dave 10, 126 Mar 18 11:29 /dev/sgx_enclave $ ./test_sgx no execute permissions on device file
If you fix that with "chmod ug+x /dev/sgx" but you leave /dev as noexec, you'll get this:
$ mount | grep "/dev .*noexec" udev on /dev type devtmpfs (rw,nosuid,noexec,...) $ ./test_sgx ERROR: mmap for exec: Operation not permitted mmap() succeeded for PROT_READ, but failed for PROT_EXEC check that user has execute permissions on /dev/sgx_enclave and that /dev does not have noexec set: 'mount | grep "/dev .*noexec"'
That can be fixed with:
mount -o remount,noexec /devESC
Hopefully, the combination of better error messages and the search engines indexing this message will help people fix their systems until we do this properly.
[ bp: Improve error messages more. ]
Intel-SIG: commit 4284f7acb78b selftests/sgx: Improve error detection and messages Backport for SGX Foundations support
Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Borislav Petkov bp@suse.de Reviewed-by: Jarkko Sakkinen jarkko@kernel.org Link: https://lore.kernel.org/r/20210318194301.11D9A984@viggo.jf.intel.com Signed-off-by: Fan Du fan.du@intel.com #openEuler_contributor Signed-off-by: Laibin Qiu qiulaibin@huawei.com --- tools/testing/selftests/sgx/load.c | 69 ++++++++++++++++++++++++------ tools/testing/selftests/sgx/main.c | 2 +- 2 files changed, 56 insertions(+), 15 deletions(-)
diff --git a/tools/testing/selftests/sgx/load.c b/tools/testing/selftests/sgx/load.c index 9d43b75aaa55..f441ac34b4d4 100644 --- a/tools/testing/selftests/sgx/load.c +++ b/tools/testing/selftests/sgx/load.c @@ -45,19 +45,19 @@ static bool encl_map_bin(const char *path, struct encl *encl)
fd = open(path, O_RDONLY); if (fd == -1) { - perror("open()"); + perror("enclave executable open()"); return false; }
ret = stat(path, &sb); if (ret) { - perror("stat()"); + perror("enclave executable stat()"); goto err; }
bin = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0); if (bin == MAP_FAILED) { - perror("mmap()"); + perror("enclave executable mmap()"); goto err; }
@@ -90,8 +90,7 @@ static bool encl_ioc_create(struct encl *encl) ioc.src = (unsigned long)secs; rc = ioctl(encl->fd, SGX_IOC_ENCLAVE_CREATE, &ioc); if (rc) { - fprintf(stderr, "SGX_IOC_ENCLAVE_CREATE failed: errno=%d\n", - errno); + perror("SGX_IOC_ENCLAVE_CREATE failed"); munmap((void *)secs->base, encl->encl_size); return false; } @@ -116,31 +115,72 @@ static bool encl_ioc_add_pages(struct encl *encl, struct encl_segment *seg)
rc = ioctl(encl->fd, SGX_IOC_ENCLAVE_ADD_PAGES, &ioc); if (rc < 0) { - fprintf(stderr, "SGX_IOC_ENCLAVE_ADD_PAGES failed: errno=%d.\n", - errno); + perror("SGX_IOC_ENCLAVE_ADD_PAGES failed"); return false; }
return true; }
+ + bool encl_load(const char *path, struct encl *encl) { + const char device_path[] = "/dev/sgx_enclave"; Elf64_Phdr *phdr_tbl; off_t src_offset; Elf64_Ehdr *ehdr; + struct stat sb; + void *ptr; int i, j; int ret; + int fd = -1;
memset(encl, 0, sizeof(*encl));
- ret = open("/dev/sgx_enclave", O_RDWR); - if (ret < 0) { - fprintf(stderr, "Unable to open /dev/sgx_enclave\n"); + fd = open(device_path, O_RDWR); + if (fd < 0) { + perror("Unable to open /dev/sgx_enclave"); + goto err; + } + + ret = stat(device_path, &sb); + if (ret) { + perror("device file stat()"); + goto err; + } + + /* + * This just checks if the /dev file has these permission + * bits set. It does not check that the current user is + * the owner or in the owning group. + */ + if (!(sb.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))) { + fprintf(stderr, "no execute permissions on device file %s\n", device_path); + goto err; + } + + ptr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_SHARED, fd, 0); + if (ptr == (void *)-1) { + perror("mmap for read"); + goto err; + } + munmap(ptr, PAGE_SIZE); + +#define ERR_MSG \ +"mmap() succeeded for PROT_READ, but failed for PROT_EXEC.\n" \ +" Check that current user has execute permissions on %s and \n" \ +" that /dev does not have noexec set: mount | grep "/dev .*noexec"\n" \ +" If so, remount it executable: mount -o remount,exec /dev\n\n" + + ptr = mmap(NULL, PAGE_SIZE, PROT_EXEC, MAP_SHARED, fd, 0); + if (ptr == (void *)-1) { + fprintf(stderr, ERR_MSG, device_path); goto err; } + munmap(ptr, PAGE_SIZE);
- encl->fd = ret; + encl->fd = fd;
if (!encl_map_bin(path, encl)) goto err; @@ -217,6 +257,8 @@ bool encl_load(const char *path, struct encl *encl) return true;
err: + if (fd != -1) + close(fd); encl_delete(encl); return false; } @@ -229,7 +271,7 @@ static bool encl_map_area(struct encl *encl) area = mmap(NULL, encl_size * 2, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (area == MAP_FAILED) { - perror("mmap"); + perror("reservation mmap()"); return false; }
@@ -268,8 +310,7 @@ bool encl_build(struct encl *encl) ioc.sigstruct = (uint64_t)&encl->sigstruct; ret = ioctl(encl->fd, SGX_IOC_ENCLAVE_INIT, &ioc); if (ret) { - fprintf(stderr, "SGX_IOC_ENCLAVE_INIT failed: errno=%d\n", - errno); + perror("SGX_IOC_ENCLAVE_INIT failed"); return false; }
diff --git a/tools/testing/selftests/sgx/main.c b/tools/testing/selftests/sgx/main.c index 724cec700926..b117bb86a73f 100644 --- a/tools/testing/selftests/sgx/main.c +++ b/tools/testing/selftests/sgx/main.c @@ -195,7 +195,7 @@ int main(int argc, char *argv[], char *envp[]) addr = mmap((void *)encl.encl_base + seg->offset, seg->size, seg->prot, MAP_SHARED | MAP_FIXED, encl.fd, 0); if (addr == MAP_FAILED) { - fprintf(stderr, "mmap() failed, errno=%d.\n", errno); + perror("mmap() segment failed"); exit(KSFT_FAIL); } }