| Message ID | CAEkJfYNguDt47=KnEUX7tLwx_46ggBx3Oh3-3dAcZxqndL_OWQ@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | drivers: scsi: fix shift-out-of-bounds in sg_build_indirect | expand |
On Tue, Apr 16, 2024 at 1:26 AM Bart Van Assche <bvanassche@acm.org> wrote: > > On 4/14/24 20:14, Sam Sun wrote: > > - num = scatter_elem_sz; > > + num = max(scatter_elem_sz, PAGE_SIZE); > > Shouldn't the following statements be modified instead of the above > statement? I think these are the only statements that can cause > scatter_elem_sz to become smaller than PAGE_SIZE: > > scatter_elem_sz = ret_sz; > scatter_elem_sz_prev = ret_sz; > Yes, these statements are the only statements that modify scatter_elem_sz. However, ret_sz will never be less than PAGE_SIZE, since it is calculated by 1 << (PAGE_SIZE + order), and order will not be less than zero. So I think these statements do not need to be modified. scatter_elem_sz is also exported to userspace by sysfs interface (macro module_param_named()), and privileged users could modify it to any int they want. So I also set the exported type to uint in this patch. Should I also change the type of scatter_elem_sz and scatter_elem_sz_prev also to uint? Best Regards, Yue
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 9d7b7db75e4b..6199481be585 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1586,7 +1586,7 @@ sg_remove_device(struct device *cl_dev, struct class_interface *cl_intf) kref_put(&sdp->d_ref, sg_device_destroy); } -module_param_named(scatter_elem_sz, scatter_elem_sz, int, S_IRUGO | S_IWUSR); +module_param_named(scatter_elem_sz, scatter_elem_sz, uint, S_IRUGO | S_IWUSR); module_param_named(def_reserved_size, def_reserved_size, int, S_IRUGO | S_IWUSR);
The get_order(0) is undefined. If scatter_elem_sz is equal or below zero, the order returned will be 52, so that PAGE_SHIFT + order is 64, which is larger than 32 bits int range, causing shift-out-of bound. scatter_elem_sz equals or below zero is not allowed in the sg_build_indirect(). UBSAN: shift-out-of-bounds in /home/sy/linux-original/drivers/scsi/sg.c:1902:13 shift exponent 64 is too large for 32-bit type 'int' CPU: 1 PID: 8078 Comm: syz-executor748 Not tainted 6.7.0-rc7 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x136/0x150 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:217 [inline] __ubsan_handle_shift_out_of_bounds+0x24b/0x430 lib/ubsan.c:387 sg_build_indirect.cold+0x1b/0x20 drivers/scsi/sg.c:1902 sg_build_reserve+0xc4/0x180 drivers/scsi/sg.c:2012 sg_add_sfp drivers/scsi/sg.c:2194 [inline] sg_open+0xde4/0x1810 drivers/scsi/sg.c:350 chrdev_open+0x269/0x770 fs/char_dev.c:414 do_dentry_open+0x6d3/0x18d0 fs/open.c:948 do_open fs/namei.c:3622 [inline] path_openat+0x1e1e/0x26d0 fs/namei.c:3779 do_filp_open+0x1c9/0x410 fs/namei.c:3809 do_sys_openat2+0x160/0x1c0 fs/open.c:1437 do_sys_open fs/open.c:1452 [inline] __do_sys_openat fs/open.c:1468 [inline] __se_sys_openat fs/open.c:1463 [inline] __x64_sys_openat+0x140/0x1f0 fs/open.c:1463 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b ---[ end trace ]--- Fix it by setting the minimum num to PAGE_SIZE, and change the type of scatter_elem_sz to uint. Reported-by: Yue Sun <samsun1006219@gmail.com> Reported by: xingwei lee <xrivendell7@gmail.com> Signed-off-by: Yue Sun <samsun1006219@gmail.com> --- drivers/scsi/sg.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) module_param_named(allow_dio, sg_allow_dio, int, S_IRUGO | S_IWUSR); @@ -1837,7 +1837,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size) if (mx_sc_elems < 0) return mx_sc_elems; /* most likely -ENOMEM */ - num = scatter_elem_sz; + num = max(scatter_elem_sz, PAGE_SIZE); if (unlikely(num != scatter_elem_sz_prev)) { if (num < PAGE_SIZE) { scatter_elem_sz = PAGE_SIZE;