4.16-stable review patch. If anyone has any objections, please let me know.
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From: Jiri Slaby jslaby@suse.cz
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@suse.cz Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Theodore Ts'o tytso@mit.edu Cc: stable@vger.kernel.org # v4.15 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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) {