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Kernel: Don't check pledges or veil against code coverage data files

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Coverage tools like LLVM's source-based coverage or GNU's --coverage
need to be able to write out coverage files from any binary, regardless
of its security posture. Not ignoring these pledges and veils means we
can't get our coverage data out without playing some serious tricks.

However this is pretty terrible for normal exeuction, so only skip these
checks when we explicitly configured userspace for coverage.
This commit is contained in:
Andrew Kaster 2022-03-04 18:05:24 -07:00 • committed by Andreas Kling
parent 5120b39d0e
commit f08e91f67e
3 changed files with 30 additions and 8 deletions
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27
Kernel/Syscalls/open.cpp
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@ -7,6 +7,7 @@
#include <Kernel/Debug.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
#include <Kernel/KLexicalPath.h>
#include <Kernel/Net/LocalSocket.h>
#include <Kernel/Process.h>
@ -27,19 +28,29 @@ ErrorOr<FlatPtr> Process::sys$open(Userspace<Syscall::SC_open_params const*> use
if (options & O_UNLINK_INTERNAL)
return EINVAL;
if (options & O_WRONLY)
TRY(require_promise(Pledge::wpath));
else if (options & O_RDONLY)
TRY(require_promise(Pledge::rpath));
auto path = TRY(get_syscall_path_argument(params.path));
if (options & O_CREAT)
TRY(require_promise(Pledge::cpath));
// Disable checking open pledges when building userspace with coverage
// so that all processes can write out coverage data even with pledges
bool skip_pledge_verification = false;
#ifdef SKIP_PATH_VALIDATION_FOR_COVERAGE_INSTRUMENTATION
if (KLexicalPath::basename(path->view()).ends_with(".profraw"sv))
skip_pledge_verification = true;
#endif
if (!skip_pledge_verification) {
if (options & O_WRONLY)
TRY(require_promise(Pledge::wpath));
else if (options & O_RDONLY)
TRY(require_promise(Pledge::rpath));
if (options & O_CREAT)
TRY(require_promise(Pledge::cpath));
}
// Ignore everything except permission bits.
mode &= 0777;
auto path = TRY(get_syscall_path_argument(params.path));
dbgln_if(IO_DEBUG, "sys$open(dirfd={}, path='{}', options={}, mode={})", dirfd, path->view(), options, mode);
auto fd_allocation = TRY(allocate_fd());