diff options
| author | Justin Stitt <justinstitt@google.com> | 2024-05-13 17:50:30 +0000 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2024-05-27 15:58:46 +0200 |
| commit | 23cc6ef6fd453b13502caae23130844e7d6ed0fe (patch) | |
| tree | 066c9e6debe7a2f96e482132c374bb107520cc77 /fs/open.c | |
| parent | 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0 (diff) | |
fs: remove accidental overflow during wraparound check
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>
Diffstat (limited to 'fs/open.c')
| -rw-r--r-- | fs/open.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/open.c b/fs/open.c index 89cafb572061..a5c4f8a0f143 100644 --- a/fs/open.c +++ b/fs/open.c @@ -247,6 +247,7 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len) { struct inode *inode = file_inode(file); long ret; + loff_t sum; if (offset < 0 || len <= 0) return -EINVAL; @@ -319,8 +320,11 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len) if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode)) return -ENODEV; - /* Check for wrap through zero too */ - if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0)) + /* Check for wraparound */ + if (check_add_overflow(offset, len, &sum)) + return -EFBIG; + + if (sum > inode->i_sb->s_maxbytes) return -EFBIG; if (!file->f_op->fallocate) |