The following commit has been merged into the x86/fpu branch of tip:
Commit-ID: 5d3b81d4d8520efe888536b6906dc10fd1a228a8
Gitweb: https://git.kernel.org/tip/5d3b81d4d8520efe888536b6906dc10fd1a228a8
Author: Benjamin Berg <benjamin.berg@xxxxxxxxx>
AuthorDate: Wed, 26 Feb 2025 14:31:36 +01:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 26 Feb 2025 15:32:34 +01:00
x86/fpu: Avoid copying dynamic FP state from init_task in arch_dup_task_struct()
The init_task instance of struct task_struct is statically allocated and
may not contain the full FP state for userspace. As such, limit the copy
to the valid area of both init_task and 'dst' and ensure all memory is
initialized.
Note that the FP state is only needed for userspace, and as such it is
entirely reasonable for init_task to not contain parts of it.
Fixes: 5aaeb5c01c5b ("x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86")
Signed-off-by: Benjamin Berg <benjamin.berg@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20250226133136.816901-1-benjamin@xxxxxxxxxxxxxxxx
----
v2:
- Fix code if arch_task_struct_size < sizeof(init_task) by using
memcpy_and_pad.
---
arch/x86/kernel/process.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 6da6769..7cb52f8 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -93,7 +93,12 @@ EXPORT_PER_CPU_SYMBOL_GPL(__tss_limit_invalid);
*/
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
- memcpy(dst, src, arch_task_struct_size);
+ /* init_task is not dynamically sized (incomplete FPU state) */
+ if (unlikely(src == &init_task))
+ memcpy_and_pad(dst, arch_task_struct_size, src, sizeof(init_task), 0);
+ else
+ memcpy(dst, src, arch_task_struct_size);
+
#ifdef CONFIG_VM86
dst->thread.vm86 = NULL;
#endif
|