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Message-Id: <0a3abf529ab9e47a136c2216af1c9d33b2b7dae3.1723334660.git.fthain@linux-m68k.org>
Date: Sun, 11 Aug 2024 10:04:20 +1000
From: Finn Thain <fthain@...ux-m68k.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Christian Brauner <brauner@...nel.org>,
Greg Ungerer <gerg@...ux-m68k.org>,
Stan Johnson <userm57@...oo.com>,
linux-m68k@...ts.linux-m68k.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2] m68k: Fix kernel_clone_args.flags in m68k_clone()
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 -EBADFD. Avoid sign-extension by casting to u32.
Cc: Stan Johnson <userm57@...oo.com>
Reported-by: Stan Johnson <userm57@...oo.com>
Closes: https://lists.debian.org/debian-68k/2024/08/msg00000.html
Fixes: 6aabc1facdb2 ("m68k: Implement copy_thread_tls()")
Signed-off-by: Finn Thain <fthain@...ux-m68k.org>
---
Changed since v1:
- Cast to u32 instead of using lower_32_bits() as suggested by Geert.
---
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
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