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[ Upstream commit d1693a7d5a38acf6424235a6070bcf5b186a360d ]
When mounting, sb->s_blocksize is used to read the boot_block without
being defined or validated. Set a dummy blocksize before attempting to
read the boot_block.
The issue can be triggered with the following syz reproducer:
mkdirat(0xffffffffffffff9c, &(0x7f0000000080)='./file1\x00', 0x0)
r4 = openat$nullb(0xffffffffffffff9c, &(0x7f0000000040), 0x121403, 0x0)
ioctl$FS_IOC_SETFLAGS(r4, 0x40081271, &(0x7f0000000980)=0x4000)
mount(&(0x7f0000000140)=@nullb, &(0x7f0000000040)='./cgroup\x00',
&(0x7f0000000000)='ntfs3\x00', 0x2208004, 0x0)
syz_clone(0x88200200, 0x0, 0x0, 0x0, 0x0, 0x0)
Here, the ioctl sets the bdev block size to 16384. During mount,
get_tree_bdev_flags() calls sb_set_blocksize(sb, block_size(bdev)),
but since block_size(bdev) > PAGE_SIZE, sb_set_blocksize() leaves
sb->s_blocksize at zero.
Later, ntfs_init_from_boot() attempts to read the boot_block while
sb->s_blocksize is still zero, which triggers the bug.
Reported-by: syzbot+f4f84b57a01d6b8364ad@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=f4f84b57a01d6b8364ad
Signed-off-by: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
[almaz.alexandrovich@paragon-software.com: changed comment style, added
return value handling]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.