squashfs metadata 2: electric boogaloo

Anatoly continues to find issues with fuzzed squashfs images.

This time, corrupt, missing, or undersized data for the page filling
wasn't checked for, because the squashfs_{copy,read}_cache() functions
did the squashfs_copy_data() call without checking the resulting data
size.

Which could result in the page cache pages being incompletely filled in,
and no error indication to the user space reading garbage data.

So make a helper function for the "fill in pages" case, because the
exact same incomplete sequence existed in two places.

[ I should have made a squashfs branch for these things, but I didn't
  intend to start doing them in the first place.

  My historical connection through cramfs is why I got into looking at
  these issues at all, and every time I (continue to) think it's a
  one-off.

  Because _this_ time is always the last time. Right?   - Linus ]

Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Tested-by: Willy Tarreau <w@1wt.eu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index fcff2e0487fef11f89724a72221090e529f0a775..cce3060650aebd74962280254155868ee4b2a591 100644 (file)
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -374,13 +374,29 @@ static int read_blocklist(struct inode *inode, int index, u64 *block)
        return squashfs_block_size(size);
 }
 
+void squashfs_fill_page(struct page *page, struct squashfs_cache_entry *buffer, int offset, int avail)
+{
+       int copied;
+       void *pageaddr;
+
+       pageaddr = kmap_atomic(page);
+       copied = squashfs_copy_data(pageaddr, buffer, offset, avail);
+       memset(pageaddr + copied, 0, PAGE_SIZE - copied);
+       kunmap_atomic(pageaddr);
+
+       flush_dcache_page(page);
+       if (copied == avail)
+               SetPageUptodate(page);
+       else
+               SetPageError(page);
+}
+
 /* Copy data into page cache  */
 void squashfs_copy_cache(struct page *page, struct squashfs_cache_entry *buffer,
        int bytes, int offset)
 {
        struct inode *inode = page->mapping->host;
        struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
-       void *pageaddr;
        int i, mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
        int start_index = page->index & ~mask, end_index = start_index | mask;
 
@@ -406,12 +422,7 @@ void squashfs_copy_cache(struct page *page, struct squashfs_cache_entry *buffer,
                if (PageUptodate(push_page))
                        goto skip_page;
 
-               pageaddr = kmap_atomic(push_page);
-               squashfs_copy_data(pageaddr, buffer, offset, avail);
-               memset(pageaddr + avail, 0, PAGE_SIZE - avail);
-               kunmap_atomic(pageaddr);
-               flush_dcache_page(push_page);
-               SetPageUptodate(push_page);
+               squashfs_fill_page(push_page, buffer, offset, avail);
 skip_page:
                unlock_page(push_page);
                if (i != page->index)

diff --git a/fs/squashfs/file_direct.c b/fs/squashfs/file_direct.c
index cb485d8e0e91b1b2ff1cb9b0330339c51c15b8a4..096990254a2eaf6e48d6ccb5d2ace4623a614b06 100644 (file)
--- a/fs/squashfs/file_direct.c
+++ b/fs/squashfs/file_direct.c
@@ -144,7 +144,6 @@ static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
        struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,
                                                 block, bsize);
        int bytes = buffer->length, res = buffer->error, n, offset = 0;
-       void *pageaddr;
 
        if (res) {
                ERROR("Unable to read page, block %llx, size %x\n", block,
@@ -159,12 +158,7 @@ static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
                if (page[n] == NULL)
                        continue;
 
-               pageaddr = kmap_atomic(page[n]);
-               squashfs_copy_data(pageaddr, buffer, offset, avail);
-               memset(pageaddr + avail, 0, PAGE_SIZE - avail);
-               kunmap_atomic(pageaddr);
-               flush_dcache_page(page[n]);
-               SetPageUptodate(page[n]);
+               squashfs_fill_page(page[n], buffer, offset, avail);
                unlock_page(page[n]);
                if (page[n] != target_page)
                        put_page(page[n]);

diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h
index 887d6d270080a6d8d945868c5bc1265d3f38f93c..d8d43724cf2ad8320e69b728f293c800d2821ec0 100644 (file)
--- a/fs/squashfs/squashfs.h
+++ b/fs/squashfs/squashfs.h
@@ -67,6 +67,7 @@ extern __le64 *squashfs_read_fragment_index_table(struct super_block *,
                                u64, u64, unsigned int);
 
 /* file.c */
+void squashfs_fill_page(struct page *, struct squashfs_cache_entry *, int, int);
 void squashfs_copy_cache(struct page *, struct squashfs_cache_entry *, int,
                                int);