4.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Slaby <jslaby@xxxxxxx>
commit fe23cb65c2c394ea306f3714a17d46ab2e6a0af1 upstream.
ext4_iomap_begin() has a bug where offset returned in the iomap
structure will be truncated to unsigned long size. On 64-bit
architectures this is fine but on 32-bit architectures obviously not.
Not many places actually use the offset stored in the iomap structure
but one of visible failures is in SEEK_HOLE / SEEK_DATA implementation.
If we create a file like:
dd if=/dev/urandom of=file bs=1k seek=8m count=1
then
lseek64("file", 0x100000000ULL, SEEK_DATA)
wrongly returns 0x100000000 on unfixed kernel while it should return
0x200000000. Avoid the overflow by proper type cast.
Fixes: 545052e9e35a ("ext4: Switch to iomap for SEEK_HOLE / SEEK_DATA")
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.15
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3524,7 +3524,7 @@ retry:
iomap->flags |= IOMAP_F_DIRTY;
iomap->bdev = inode->i_sb->s_bdev;
iomap->dax_dev = sbi->s_daxdev;
- iomap->offset = first_block << blkbits;
+ iomap->offset = (u64)first_block << blkbits;
iomap->length = (u64)map.m_len << blkbits;
if (ret == 0) {