On 2023/4/18 11:13, HORIGUCHI NAOYA(堀口 直也) wrote:
On Mon, Apr 17, 2023 at 12:53:23PM +0800, Kefeng Wang wrote:
The dump_user_range() is used to copy the user page to a coredump file,
but if a hardware memory error occurred during copy, which called from
__kernel_write_iter() in dump_user_range(), it crashes,
CPU: 112 PID: 7014 Comm: mca-recover Not tainted 6.3.0-rc2 #425
pc : __memcpy+0x110/0x260
lr : _copy_from_iter+0x3bc/0x4c8
...
Call trace:
__memcpy+0x110/0x260
copy_page_from_iter+0xcc/0x130
pipe_write+0x164/0x6d8
__kernel_write_iter+0x9c/0x210
dump_user_range+0xc8/0x1d8
elf_core_dump+0x308/0x368
do_coredump+0x2e8/0xa40
get_signal+0x59c/0x788
do_signal+0x118/0x1f8
do_notify_resume+0xf0/0x280
el0_da+0x130/0x138
el0t_64_sync_handler+0x68/0xc0
el0t_64_sync+0x188/0x190
Generally, the '->write_iter' of file ops will use copy_page_from_iter()
and copy_page_from_iter_atomic(), change memcpy() to copy_mc_to_kernel()
in both of them to handle #MC during source read, which stop coredump
processing and kill the task instead of kernel panic, but the source
address may not always a user address, so introduce a new copy_mc flag in
struct iov_iter{} to indicate that the iter could do a safe memory copy,
also introduce the helpers to set/cleck the flag, for now, it's only
used in coredump's dump_user_range(), but it could expand to any other
scenarios to fix the similar issue.
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Tong Tiangen <tongtiangen@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
v2:
- move the helper functions under pre-existing CONFIG_ARCH_HAS_COPY_MC
- reposition the copy_mc in struct iov_iter for easy merge, suggested
by Andrew Morton
- drop unnecessary clear flag helper
- fix checkpatch warning
fs/coredump.c | 1 +
include/linux/uio.h | 16 ++++++++++++++++
lib/iov_iter.c | 17 +++++++++++++++--
3 files changed, 32 insertions(+), 2 deletions(-)
...
@@ -371,6 +372,14 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
#endif /* CONFIG_ARCH_HAS_COPY_MC */
+static void *memcpy_from_iter(struct iov_iter *i, void *to, const void *from,
+ size_t size)
+{
+ if (iov_iter_is_copy_mc(i))
+ return (void *)copy_mc_to_kernel(to, from, size);
Is it helpful to call memory_failure_queue() if copy_mc_to_kernel() fails
due to a memory error?
For dump_user_range(), the task is dying, if copy incomplete size, the
coredump will fail and task will exit, also memory_failure will
be called by kill_me_maybe(),
CPU: 0 PID: 1418 Comm: test Tainted: G M 6.3.0-rc5 #29
Call Trace:
<TASK>
dump_stack_lvl+0x37/0x50
memory_failure+0x51/0x970
kill_me_maybe+0x5b/0xc0
task_work_run+0x5a/0x90
exit_to_user_mode_prepare+0x194/0x1a0
irqentry_exit_to_user_mode+0x9/0x30
noist_exc_machine_check+0x40/0x80
asm_exc_machine_check+0x33/0x40
Thanks,
Naoya Horiguchi
+ return memcpy(to, from, size);
+}
+
size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
