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Filename Latest commit message Latest commit date
Carlos Maiolino dce30ca9e3 fs: fix guard_bio_eod to check for real EOD errors
guard_bio_eod() can truncate a segment in bio to allow it to do IO on
odd last sectors of a device.

It already checks if the IO starts past EOD, but it does not consider
the possibility of an IO request starting within device boundaries can
contain more than one segment past EOD.

In such cases, truncated_bytes can be bigger than PAGE_SIZE, and will
underflow bvec->bv_len.

Fix this by checking if truncated_bytes is lower than PAGE_SIZE.

This situation has been found on filesystems such as isofs and vfat,
which doesn't check the device size before mount, if the device is
smaller than the filesystem itself, a readahead on such filesystem,
which spans EOD, can trigger this situation, leading a call to
zero_user() with a wrong size possibly corrupting memory.

I didn't see any crash, or didn't let the system run long enough to
check if memory corruption will be hit somewhere, but adding
instrumentation to guard_bio_end() to check truncated_bytes size, was
enough to see the error.

The following script can trigger the error.

MNT=/mnt
IMG=./DISK.img
DEV=/dev/loop0

mkfs.vfat $IMG
mount $IMG $MNT
cp -R /etc $MNT &> /dev/null
umount $MNT

losetup -D

losetup --find --show --sizelimit 16247280 $IMG
mount $DEV $MNT

find $MNT -type f -exec cat {} + >/dev/null

Kudos to Eric Sandeen for coming up with the reproducer above

Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-02-28 13:59:41 -07:00
arch Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:57:42 -08:00
block blk-mq: use HCTX_TYPE_DEFAULT but not 0 to index blk_mq_tag_set->map 2019-02-28 13:57:32 -07:00
certs
crypto
Documentation fs: add an iopoll method to struct file_operations 2019-02-24 08:20:17 -07:00
drivers loop: set GENHD_FL_NO_PART_SCAN after blkdev_reread_part() 2019-02-22 15:51:22 -07:00
firmware
fs fs: fix guard_bio_eod to check for real EOD errors 2019-02-28 13:59:41 -07:00
include block: optimize bvec iteration in bvec_iter_advance 2019-02-28 13:49:22 -07:00
init
ipc
kernel Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:48:18 -08:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 11:21:54 -08:00
LICENSES
mm
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-08 11:21:54 -08:00
samples
scripts
security
sound sound fixes for 5.0-rc6 2019-02-07 08:33:56 +00:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-02-10 09:48:18 -08:00
usr
virt kvm: fix kvm_ioctl_create_device() reference counting (CVE-2019-6974) 2019-02-07 19:02:38 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2019-02-09 13:43:12 -08:00
Makefile Linux 5.0-rc6 2019-02-10 14:42:20 -08:00
README

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.