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eCryptfs: Infinite loop due to overflow in ecryptfs_write()

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ecryptfs_write() can enter an infinite loop when truncating a file to a
size larger than 4G. This only happens on architectures where size_t is
represented by 32 bits.

This was caused by a size_t overflow due to it incorrectly being used to
store the result of a calculation which uses potentially large values of
type loff_t.

[tyhicks@canonical.com: rewrite subject and commit message]
Signed-off-by: Li Wang <liwang@nudt.edu.cn>
Signed-off-by: Yunchuan Wen <wenyunchuan@kylinos.com.cn>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
This commit is contained in:
Li Wang 2012-01-19 09:44:36 +08:00 committed by Tyler Hicks
parent 48399c0b0e
commit 684a3ff7e6
1 changed files with 2 additions and 2 deletions
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4
fs/ecryptfs/read_write.c
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@ -130,13 +130,13 @@ int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT); pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK); size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page); size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
size_t total_remaining_bytes = ((offset + size) - pos); loff_t total_remaining_bytes = ((offset + size) - pos);
if (num_bytes > total_remaining_bytes) if (num_bytes > total_remaining_bytes)
num_bytes = total_remaining_bytes; num_bytes = total_remaining_bytes;
if (pos < offset) { if (pos < offset) {
/* remaining zeros to write, up to destination offset */ /* remaining zeros to write, up to destination offset */
size_t total_remaining_zeros = (offset - pos); loff_t total_remaining_zeros = (offset - pos);
if (num_bytes > total_remaining_zeros) if (num_bytes > total_remaining_zeros)
num_bytes = total_remaining_zeros; num_bytes = total_remaining_zeros;