mm: hwpoison: coredump: support recovery from dump_user_range()

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.

Link: https://lkml.kernel.org/r/20230417045323.11054-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Tong Tiangen <tongtiangen@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/coredump.c b/fs/coredump.c
index 5df1e6e1eb2bea1ff98e69f3056baa4aba02cd11..ece7badf701bc2f917796aa565b478b21c5ce104 100644 (file)
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -882,6 +882,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
        pos = file->f_pos;
        bvec_set_page(&bvec, page, PAGE_SIZE, 0);
        iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE);
+       iov_iter_set_copy_mc(&iter);
        n = __kernel_write_iter(cprm->file, &iter, &pos);
        if (n != PAGE_SIZE)
                return 0;

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 3d386849a7584906453a43431316990bababd6dd..044c1d8c230cfa2600da3edc10226d39ba287c4b 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -42,6 +42,7 @@ struct iov_iter_state {
 
 struct iov_iter {
        u8 iter_type;
+       bool copy_mc;
        bool nofault;
        bool data_source;
        bool user_backed;
@@ -256,8 +257,22 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
 
 #ifdef CONFIG_ARCH_HAS_COPY_MC
 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
+static inline void iov_iter_set_copy_mc(struct iov_iter *i)
+{
+       i->copy_mc = true;
+}
+
+static inline bool iov_iter_is_copy_mc(const struct iov_iter *i)
+{
+       return i->copy_mc;
+}
 #else
 #define _copy_mc_to_iter _copy_to_iter
+static inline void iov_iter_set_copy_mc(struct iov_iter *i) { }
+static inline bool iov_iter_is_copy_mc(const struct iov_iter *i)
+{
+       return false;
+}
 #endif
 
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
@@ -380,6 +395,7 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
        WARN_ON(direction & ~(READ | WRITE));
        *i = (struct iov_iter) {
                .iter_type = ITER_UBUF,
+               .copy_mc = false,
                .user_backed = true,
                .data_source = direction,
                .ubuf = buf,

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index c3dbe994112c671783e703057c006846cd561333..960223ed91991ab83edcebe918d25b0a4f555e2f 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -434,6 +434,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
        WARN_ON(direction & ~(READ | WRITE));
        *i = (struct iov_iter) {
                .iter_type = ITER_IOVEC,
+               .copy_mc = false,
                .nofault = false,
                .user_backed = true,
                .data_source = direction,
@@ -630,6 +631,14 @@ 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);
+       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))
@@ -639,7 +648,7 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
                might_fault();
        iterate_and_advance(i, bytes, base, len, off,
                copyin(addr + off, base, len),
-               memcpy(addr + off, base, len)
+               memcpy_from_iter(i, addr + off, base, len)
        )
 
        return bytes;
@@ -862,7 +871,7 @@ size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t byt
        }
        iterate_and_advance(i, bytes, base, len, off,
                copyin(p + off, base, len),
-               memcpy(p + off, base, len)
+               memcpy_from_iter(i, p + off, base, len)
        )
        kunmap_atomic(kaddr);
        return bytes;
@@ -1043,6 +1052,7 @@ void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
        WARN_ON(direction & ~(READ | WRITE));
        *i = (struct iov_iter){
                .iter_type = ITER_KVEC,
+               .copy_mc = false,
                .data_source = direction,
                .kvec = kvec,
                .nr_segs = nr_segs,
@@ -1059,6 +1069,7 @@ void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
        WARN_ON(direction & ~(READ | WRITE));
        *i = (struct iov_iter){
                .iter_type = ITER_BVEC,
+               .copy_mc = false,
                .data_source = direction,
                .bvec = bvec,
                .nr_segs = nr_segs,
@@ -1105,6 +1116,7 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
        BUG_ON(direction & ~1);
        *i = (struct iov_iter) {
                .iter_type = ITER_XARRAY,
+               .copy_mc = false,
                .data_source = direction,
                .xarray = xarray,
                .xarray_start = start,
@@ -1128,6 +1140,7 @@ void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
        BUG_ON(direction != READ);
        *i = (struct iov_iter){
                .iter_type = ITER_DISCARD,
+               .copy_mc = false,
                .data_source = false,
                .count = count,
                .iov_offset = 0