Stan Johnson recently reported a failure from the 'dump' command: DUMP: Date of this level 0 dump: Fri Aug 9 23:37:15 2024 DUMP: Dumping /dev/sda (an unlisted file system) to /dev/null DUMP: Label: none DUMP: Writing 10 Kilobyte records DUMP: mapping (Pass I) [regular files] DUMP: mapping (Pass II) [directories] DUMP: estimated 3595695 blocks. DUMP: Context save fork fails in parent 671 The dump program uses the clone syscall with the CLONE_IO flag, that is, flags == 0x80000000. When that value is promoted from long int to u64 by m68k_clone(), it undergoes sign-extension. The new value includes CLONE_INTO_CGROUP so the validation in cgroup_css_set_fork() fails and the syscall returns -EBADF. Avoid sign-extension by casting to u32. Cc: Stan Johnson <userm57@xxxxxxxxx> Reported-by: Stan Johnson <userm57@xxxxxxxxx> Closes: https://lists.debian.org/debian-68k/2024/08/msg00000.html Fixes: 6aabc1facdb2 ("m68k: Implement copy_thread_tls()") Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxx> --- Changed since v1: - Cast to u32 instead of using lower_32_bits() as suggested by Geert. Changed since v2: - Commit log ammended with -EBADF instead of -EBADFD. --- arch/m68k/kernel/process.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c index 2584e94e2134..fda7eac23f87 100644 --- a/arch/m68k/kernel/process.c +++ b/arch/m68k/kernel/process.c @@ -117,7 +117,7 @@ asmlinkage int m68k_clone(struct pt_regs *regs) { /* regs will be equal to current_pt_regs() */ struct kernel_clone_args args = { - .flags = regs->d1 & ~CSIGNAL, + .flags = (u32)(regs->d1) & ~CSIGNAL, .pidfd = (int __user *)regs->d3, .child_tid = (int __user *)regs->d4, .parent_tid = (int __user *)regs->d3, -- 2.39.5
