On Mon, Mar 25, 2024 at 8:57 PM Sam Sun <samsun1006219@xxxxxxxxx> wrote: > > Dear developers and maintainers, > > We encountered a shift-out-of-bounds bug while using our modified > Syzkaller. It is tested against linux kernel 6.9-rc1. Kernel config > and C repro are attached to this email. The UBSAN report is listed > below. > > ================================================================================ > 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 > RIP: 0033:0x7f48cf37f80b > Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 > c0 75 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d > 00 f0 ff ff 0f 87 91 00 00 00 48 8b 4c 24 28 64 48 33 0c 25 > RSP: 002b:00007ffd29cd7d40 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f48cf37f80b > RDX: 0000000000000041 RSI: 00007ffd29cd7dc0 RDI: 00000000ffffff9c > RBP: 00007ffd29cd7dc0 R08: 000000000000ffff R09: 00007ffd29cd7c50 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000041 > R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 > </TASK> > ================================================================================ > > If you have any questions, please contact us. > Reported by: Yue Sun <samsun1006219@xxxxxxxxx> > Reported by: xingwei lee <xrivendell7@xxxxxxxxx> > > Best Regards, > Yue We further analyzed the root cause of this bug. In function sg_build_indirect of drivers/scsi/sg.c, variable order of line 1900 is calculated out using get_order(num), and num comes from scatter_elem_sz. 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. This bug is tested and still remains in the latest upstream linux (6.9-rc3). If you have any questions, please contact us. Best, Yue
