23cc6ef6fd
Running syzkaller with the newly enabled signed integer overflow sanitizer produces this report: [ 195.401651] ------------[ cut here ]------------ [ 195.404808] UBSAN: signed-integer-overflow in ../fs/open.c:321:15 [ 195.408739] 9223372036854775807 + 562984447377399 cannot be represented in type 'loff_t' (aka 'long long') [ 195.414683] CPU: 1 PID: 703 Comm: syz-executor.0 Not tainted 6.8.0-rc2-00039-g14de58dbe653-dirty #11 [ 195.420138] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 195.425804] Call Trace: [ 195.427360] <TASK> [ 195.428791] dump_stack_lvl+0x93/0xd0 [ 195.431150] handle_overflow+0x171/0x1b0 [ 195.433640] vfs_fallocate+0x459/0x4f0 ... [ 195.490053] ------------[ cut here ]------------ [ 195.493146] UBSAN: signed-integer-overflow in ../fs/open.c:321:61 [ 195.497030] 9223372036854775807 + 562984447377399 cannot be represented in type 'loff_t' (aka 'long long) [ 195.502940] CPU: 1 PID: 703 Comm: syz-executor.0 Not tainted 6.8.0-rc2-00039-g14de58dbe653-dirty #11 [ 195.508395] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 195.514075] Call Trace: [ 195.515636] <TASK> [ 195.517000] dump_stack_lvl+0x93/0xd0 [ 195.519255] handle_overflow+0x171/0x1b0 [ 195.521677] vfs_fallocate+0x4cb/0x4f0 [ 195.524033] __x64_sys_fallocate+0xb2/0xf0 Historically, the signed integer overflow sanitizer did not work in the kernel due to its interaction with `-fwrapv` but this has since been changed [1] in the newest version of Clang. It was re-enabled in the kernel with Commit 557f8c582a9ba8ab ("ubsan: Reintroduce signed overflow sanitizer"). Let's use the check_add_overflow helper to first verify the addition stays within the bounds of its type (long long); then we can use that sum for the following check. Link: https://github.com/llvm/llvm-project/pull/82432 [1] Closes: https://github.com/KSPP/linux/issues/356 Cc: linux-hardening@vger.kernel.org Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Justin Stitt <justinstitt@google.com> Link: https://lore.kernel.org/r/20240513-b4-sio-vfs_fallocate-v2-1-db415872fb16@google.com Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Christian Brauner <brauner@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 reStructuredText 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.