On Mon, 12 Dec 2016, Andrey Konovalov wrote: > On Mon, Dec 12, 2016 at 9:31 PM, Andrey Konovalov <andreyk...@google.com> > wrote: > > Hi! > > > > While running the syzkaller fuzzer I've got the following error report. > > > > The issue is that the len argument is not checked for being too big. > > > > WARNING: CPU: 1 PID: 9935 at mm/page_alloc.c:3511 > > __alloc_pages_nodemask+0x159c/0x1e20 > > Kernel panic - not syncing: panic_on_warn set ... > > > > CPU: 1 PID: 9935 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #34 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > > ffff88006949f2c8 ffffffff81f96b8a ffffffff00000200 1ffff1000d293dec > > ffffed000d293de4 0000000000000a06 0000000041b58ab3 ffffffff8598b510 > > ffffffff81f968f8 0000000041b58ab3 ffffffff85942a58 ffffffff81432860 > > Call Trace: > > [< inline >] __dump_stack lib/dump_stack.c:15 > > [<ffffffff81f96b8a>] dump_stack+0x292/0x398 lib/dump_stack.c:51 > > [<ffffffff8168c88e>] panic+0x1cb/0x3a9 kernel/panic.c:179 > > [<ffffffff812b80b4>] __warn+0x1c4/0x1e0 kernel/panic.c:542 > > [<ffffffff812b831c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585 > > [< inline >] __alloc_pages_slowpath mm/page_alloc.c:3511 > > [<ffffffff816c08ac>] __alloc_pages_nodemask+0x159c/0x1e20 > > mm/page_alloc.c:3781 > > [<ffffffff817cde17>] alloc_pages_current+0x1c7/0x6b0 mm/mempolicy.c:2072 > > [< inline >] alloc_pages include/linux/gfp.h:469 > > [<ffffffff8172fd8f>] kmalloc_order+0x1f/0x70 mm/slab_common.c:1015 > > [<ffffffff8172fdff>] kmalloc_order_trace+0x1f/0x160 mm/slab_common.c:1026 > > [< inline >] kmalloc_large include/linux/slab.h:422 > > [<ffffffff817e01f0>] __kmalloc+0x210/0x2d0 mm/slub.c:3723 > > [< inline >] kmalloc include/linux/slab.h:495 > > [<ffffffff832262a7>] ep_write_iter+0x167/0xb50 > > drivers/usb/gadget/legacy/inode.c:664 > > [< inline >] new_sync_write fs/read_write.c:499 > > [<ffffffff817fdcd3>] __vfs_write+0x483/0x760 fs/read_write.c:512 > > [<ffffffff817ff720>] vfs_write+0x170/0x4e0 fs/read_write.c:560 > > [< inline >] SYSC_write fs/read_write.c:607 > > [<ffffffff81803b2b>] SyS_write+0xfb/0x230 fs/read_write.c:599 > > [<ffffffff84f47ec1>] entry_SYSCALL_64_fastpath+0x1f/0xc2 > > Dumping ftrace buffer: > > (ftrace buffer empty) > > Kernel Offset: disabled
I'm not an expert in this area, but it seems like length checking of I/O operations should be done in a more central location, like the VFS, rather than in a million different drivers. Anyway, it's not a big deal if the memory allocation fails. Users who try to transfer large amounts of data at once should expect that sometimes it won't work. Alan Stern
