mm: shmem: don't truncate page if memory failure happens

commit a7605426666196c5a460dd3de6f8dac1d3c21f00 upstream.

The current behavior of memory failure is to truncate the page cache
regardless of dirty or clean.  If the page is dirty the later access
will get the obsolete data from disk without any notification to the
users.  This may cause silent data loss.  It is even worse for shmem
since shmem is in-memory filesystem, truncating page cache means
discarding data blocks.  The later read would return all zero.

The right approach is to keep the corrupted page in page cache, any
later access would return error for syscalls or SIGBUS for page fault,
until the file is truncated, hole punched or removed.  The regular
storage backed filesystems would be more complicated so this patch is
focused on shmem.  This also unblock the support for soft offlining
shmem THP.

[akpm@linux-foundation.org: coding style fixes]
[arnd@arndb.de: fix uninitialized variable use in me_pagecache_clean()]
Link: https://lkml.kernel.org/r/20211022064748.4173718-1-arnd@kernel.org
[Fix invalid pointer dereference in shmem_read_mapping_page_gfp() with a
 slight different implementation from what Ajay Garg <ajaygargnsit@gmail.com>
 and Muchun Song <songmuchun@bytedance.com> proposed and reworked the
 error handling of shmem_write_begin() suggested by Linus]
Link: https://lore.kernel.org/linux-mm/20211111084617.6746-1-ajaygargnsit@gmail.com/
Link: https://lkml.kernel.org/r/20211020210755.23964-6-shy828301@gmail.com
Link: https://lkml.kernel.org/r/20211116193247.21102-1-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ajay Garg <ajaygargnsit@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Andy Lavr <andy.lavr@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 94fa250ea55cd4eea8049011ea4045343547ebd8)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 8564f3071233a7e3b616d1d74a39f47e5a781875..85b1a77e3a99a19f8d65ead7d6ca463efa1e0e5d 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -57,6 +57,7 @@
 #include <linux/ratelimit.h>
 #include <linux/page-isolation.h>
 #include <linux/pagewalk.h>
+#include <linux/shmem_fs.h>
 #include "internal.h"
 #include "ras/ras_event.h"
 
@@ -871,6 +872,7 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p)
 {
        int ret;
        struct address_space *mapping;
+       bool extra_pins;
 
        delete_from_lru_cache(p);
 
@@ -899,18 +901,24 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p)
                goto out;
        }
 
+       /*
+        * The shmem page is kept in page cache instead of truncating
+        * so is expected to have an extra refcount after error-handling.
+        */
+       extra_pins = shmem_mapping(mapping);
+
        /*
         * Truncation is a bit tricky. Enable it per file system for now.
         *
         * Open: to take i_rwsem or not for this? Right now we don't.
         */
        ret = truncate_error_page(p, page_to_pfn(p), mapping);
+       if (has_extra_refcount(ps, p, extra_pins))
+               ret = MF_FAILED;
+
 out:
        unlock_page(p);
 
-       if (has_extra_refcount(ps, p, false))
-               ret = MF_FAILED;
-
        return ret;
 }
 

diff --git a/mm/shmem.c b/mm/shmem.c
index 0556cb5b6de6a6da4b626ba11cfb487a2d363f22..3b0d78da9cd4d4e999f4080944306b4ad8df6bde 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2463,6 +2463,7 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
        struct inode *inode = mapping->host;
        struct shmem_inode_info *info = SHMEM_I(inode);
        pgoff_t index = pos >> PAGE_SHIFT;
+       int ret = 0;
 
        /* i_rwsem is held by caller */
        if (unlikely(info->seals & (F_SEAL_GROW |
@@ -2473,7 +2474,19 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
                        return -EPERM;
        }
 
-       return shmem_getpage(inode, index, pagep, SGP_WRITE);
+       ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
+
+       if (ret)
+               return ret;
+
+       if (PageHWPoison(*pagep)) {
+               unlock_page(*pagep);
+               put_page(*pagep);
+               *pagep = NULL;
+               return -EIO;
+       }
+
+       return 0;
 }
 
 static int
@@ -2560,6 +2573,12 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
                        if (sgp == SGP_CACHE)
                                set_page_dirty(page);
                        unlock_page(page);
+
+                       if (PageHWPoison(page)) {
+                               put_page(page);
+                               error = -EIO;
+                               break;
+                       }
                }
 
                /*
@@ -3121,7 +3140,8 @@ static const char *shmem_get_link(struct dentry *dentry,
                page = find_get_page(inode->i_mapping, 0);
                if (!page)
                        return ERR_PTR(-ECHILD);
-               if (!PageUptodate(page)) {
+               if (PageHWPoison(page) ||
+                   !PageUptodate(page)) {
                        put_page(page);
                        return ERR_PTR(-ECHILD);
                }
@@ -3129,6 +3149,13 @@ static const char *shmem_get_link(struct dentry *dentry,
                error = shmem_getpage(inode, 0, &page, SGP_READ);
                if (error)
                        return ERR_PTR(error);
+               if (!page)
+                       return ERR_PTR(-ECHILD);
+               if (PageHWPoison(page)) {
+                       unlock_page(page);
+                       put_page(page);
+                       return ERR_PTR(-ECHILD);
+               }
                unlock_page(page);
        }
        set_delayed_call(done, shmem_put_link, page);
@@ -3779,6 +3806,13 @@ static void shmem_destroy_inodecache(void)
        kmem_cache_destroy(shmem_inode_cachep);
 }
 
+/* Keep the page in page cache instead of truncating it */
+static int shmem_error_remove_page(struct address_space *mapping,
+                                  struct page *page)
+{
+       return 0;
+}
+
 const struct address_space_operations shmem_aops = {
        .writepage      = shmem_writepage,
        .set_page_dirty = __set_page_dirty_no_writeback,
@@ -3789,7 +3823,7 @@ const struct address_space_operations shmem_aops = {
 #ifdef CONFIG_MIGRATION
        .migratepage    = migrate_page,
 #endif
-       .error_remove_page = generic_error_remove_page,
+       .error_remove_page = shmem_error_remove_page,
 };
 EXPORT_SYMBOL(shmem_aops);
 
@@ -4198,9 +4232,14 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
        error = shmem_getpage_gfp(inode, index, &page, SGP_CACHE,
                                  gfp, NULL, NULL, NULL);
        if (error)
-               page = ERR_PTR(error);
-       else
-               unlock_page(page);
+               return ERR_PTR(error);
+
+       unlock_page(page);
+       if (PageHWPoison(page)) {
+               put_page(page);
+               return ERR_PTR(-EIO);
+       }
+
        return page;
 #else
        /*

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index d0a7271a6cd5020b34eb390c575ea87e844d09ee..caa13abe0c56b976c220667e22f036a58efbafc5 100644 (file)
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -238,6 +238,11 @@ static int mcontinue_atomic_pte(struct mm_struct *dst_mm,
                goto out;
        }
 
+       if (PageHWPoison(page)) {
+               ret = -EIO;
+               goto out_release;
+       }
+
        ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
                                       page, false, wp_copy);
        if (ret)