syzbot reported a shift-out-of-bounds in sg_build_indirect. [1] The reproducer changes the value of scatter_elem_sz to 0 before executing the open operation to open "/dev/sg0", which leads to [1]. When the value of num is 0, set its value to PAGE_SIZE to avoid this oob. [1] UBSAN: shift-out-of-bounds in drivers/scsi/sg.c:1897:13 shift exponent 64 is too large for 32-bit type 'int' CPU: 1 UID: 0 PID: 5832 Comm: syz-executor361 Not tainted 6.14.0-rc2-syzkaller-00185-g128c8f96eb86 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:231 [inline] __ubsan_handle_shift_out_of_bounds+0x24f/0x3f0 lib/ubsan.c:468 sg_build_indirect.cold+0x1b/0x20 drivers/scsi/sg.c:1897 sg_build_reserve+0xc4/0x180 drivers/scsi/sg.c:2007 sg_add_sfp drivers/scsi/sg.c:2189 [inline] sg_open+0xc37/0x1910 drivers/scsi/sg.c:348 chrdev_open+0x237/0x6a0 fs/char_dev.c:414 do_dentry_open+0x735/0x1c40 fs/open.c:956 vfs_open+0x82/0x3f0 fs/open.c:1086 do_open fs/namei.c:3830 [inline] path_openat+0x1e88/0x2d80 fs/namei.c:3989 do_filp_open+0x20c/0x470 fs/namei.c:4016 do_sys_openat2+0x17a/0x1e0 fs/open.c:1428 do_sys_open fs/open.c:1443 [inline] __do_sys_openat fs/open.c:1459 [inline] __se_sys_openat fs/open.c:1454 [inline] __x64_sys_openat+0x175/0x210 fs/open.c:1454 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Reported-by: syzbot+270f1c719ee7baab9941@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://syzkaller.appspot.com/bug?extid=270f1c719ee7baab9941 Signed-off-by: Edward Adam Davis <eadavis@xxxxxx> --- drivers/scsi/sg.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index effb7e768165..a9c445b7dab3 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1888,6 +1888,8 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size) if (num < PAGE_SIZE) { scatter_elem_sz = PAGE_SIZE; scatter_elem_sz_prev = PAGE_SIZE; + if (!num) + num = PAGE_SIZE; } else scatter_elem_sz_prev = num; } -- 2.43.0
