diff options
| author | Benjamin Berg <benjamin.berg@intel.com> | 2025-01-13 10:41:07 +0100 |
|---|---|---|
| committer | Richard Weinberger <richard@nod.at> | 2025-02-12 23:40:45 +0100 |
| commit | f82a9e7b9fa922bb9cccb00aae684a27b79e6df7 (patch) | |
| tree | 333f0d07cf0ee807ebd924ddedd87e7ab6b114a3 | |
| parent | 3c2fc7434d90338cf4c1b37bc95994208d23bfc6 (diff) | |
um: fix execve stub execution on old host OSs
The stub execution uses the somewhat new close_range and execveat
syscalls. Of these two, the execveat call is essential, but the
close_range call is more about stub process hygiene rather than safety
(and its result is ignored).
Replace both calls with a raw syscall as older machines might not have a
recent enough kernel for close_range (with CLOSE_RANGE_CLOEXEC) or a
libc that does not yet expose both of the syscalls.
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Reported-by: Glenn Washburn <development@efficientek.com>
Closes: https://lore.kernel.org/20250108022404.05e0de1e@crass-HP-ZBook-15-G2
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250113094107.674738-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
| -rw-r--r-- | arch/um/os-Linux/skas/process.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c index f683cfc9e51a..e2f8f156402f 100644 --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -181,6 +181,10 @@ extern char __syscall_stub_start[]; static int stub_exe_fd; +#ifndef CLOSE_RANGE_CLOEXEC +#define CLOSE_RANGE_CLOEXEC (1U << 2) +#endif + static int userspace_tramp(void *stack) { char *const argv[] = { "uml-userspace", NULL }; @@ -202,8 +206,12 @@ static int userspace_tramp(void *stack) init_data.stub_data_fd = phys_mapping(uml_to_phys(stack), &offset); init_data.stub_data_offset = MMAP_OFFSET(offset); - /* Set CLOEXEC on all FDs and then unset on all memory related FDs */ - close_range(0, ~0U, CLOSE_RANGE_CLOEXEC); + /* + * Avoid leaking unneeded FDs to the stub by setting CLOEXEC on all FDs + * and then unsetting it on all memory related FDs. + * This is not strictly necessary from a safety perspective. + */ + syscall(__NR_close_range, 0, ~0U, CLOSE_RANGE_CLOEXEC); fcntl(init_data.stub_data_fd, F_SETFD, 0); for (iomem = iomem_regions; iomem; iomem = iomem->next) @@ -224,7 +232,9 @@ static int userspace_tramp(void *stack) if (ret != sizeof(init_data)) exit(4); - execveat(stub_exe_fd, "", argv, NULL, AT_EMPTY_PATH); + /* Raw execveat for compatibility with older libc versions */ + syscall(__NR_execveat, stub_exe_fd, (unsigned long)"", + (unsigned long)argv, NULL, AT_EMPTY_PATH); exit(5); } |