4.4-stable review patch. If anyone has any objections, please let me know.
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From: Mike Kravetz mike.kravetz@oracle.com
commit 045c7a3f53d9403b62d396b6d051c4be5044cdb4 upstream.
If mmap() maps a file, it can be passed an offset into the file at which the mapping is to start. Offset could be a negative value when represented as a loff_t. The offset plus length will be used to update the file size (i_size) which is also a loff_t.
Validate the value of offset and offset + length to make sure they do not overflow and appear as negative.
Found by syzcaller with commit ff8c0c53c475 ("mm/hugetlb.c: don't call region_abort if region_chg fails") applied. Prior to this commit, the overflow would still occur but we would luckily return ENOMEM.
To reproduce:
mmap(0, 0x2000, 0, 0x40021, 0xffffffffffffffffULL, 0x8000000000000000ULL);
Resulted in,
kernel BUG at mm/hugetlb.c:742! Call Trace: hugetlbfs_evict_inode+0x80/0xa0 evict+0x24a/0x620 iput+0x48f/0x8c0 dentry_unlink_inode+0x31f/0x4d0 __dentry_kill+0x292/0x5e0 dput+0x730/0x830 __fput+0x438/0x720 ____fput+0x1a/0x20 task_work_run+0xfe/0x180 exit_to_usermode_loop+0x133/0x150 syscall_return_slowpath+0x184/0x1c0 entry_SYSCALL_64_fastpath+0xab/0xad
Fixes: ff8c0c53c475 ("mm/hugetlb.c: don't call region_abort if region_chg fails") Link: http://lkml.kernel.org/r/1491951118-30678-1-git-send-email-mike.kravetz@orac... Reported-by: Vegard Nossum vegard.nossum@oracle.com Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Hillf Danton hillf.zj@alibaba-inc.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Michal Hocko mhocko@suse.com Cc: "Kirill A . Shutemov" kirill.shutemov@linux.intel.com Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/hugetlbfs/inode.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
--- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -136,17 +136,26 @@ static int hugetlbfs_file_mmap(struct fi vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND; vma->vm_ops = &hugetlb_vm_ops;
+ /* + * Offset passed to mmap (before page shift) could have been + * negative when represented as a (l)off_t. + */ + if (((loff_t)vma->vm_pgoff << PAGE_SHIFT) < 0) + return -EINVAL; + if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT)) return -EINVAL;
vma_len = (loff_t)(vma->vm_end - vma->vm_start); + len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); + /* check for overflow */ + if (len < vma_len) + return -EINVAL;
mutex_lock(&inode->i_mutex); file_accessed(file);
ret = -ENOMEM; - len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); - if (hugetlb_reserve_pages(inode, vma->vm_pgoff >> huge_page_order(h), len >> huge_page_shift(h), vma, @@ -155,7 +164,7 @@ static int hugetlbfs_file_mmap(struct fi
ret = 0; if (vma->vm_flags & VM_WRITE && inode->i_size < len) - inode->i_size = len; + i_size_write(inode, len); out: mutex_unlock(&inode->i_mutex);