Hello,
On (11/07/17 17:39), Fengguang Wu wrote:
> [ 22.184920] Freeing unused kernel memory: 824K
> [ 22.199198] Freeing unused kernel memory: 1436K
> [ 22.228460] x86/mm: Checked W+X mappings: passed, no W+X pages found.
> [ 22.230474] rodata_test: all tests were successful
> [ 22.254830]
> ==================================================================
> [ 22.257125] BUG: KASAN: slab-out-of-bounds in copyin+0xea/0x170
> [ 22.258648] Write of size 26 at addr ffff880013432540 by task init/1
> [ 22.260272]
> [ 22.260860] CPU: 0 PID: 1 Comm: init Not tainted 4.14.0-rc8 #14
> [ 22.262379] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 1.10.2-1 04/01/2014
> [ 22.264441] Call Trace:
> [ 22.265206] dump_stack+0x5d/0x81
> [ 22.266147] print_address_description+0xa7/0x280
> [ 22.267369] ? copyin+0xea/0x170
> [ 22.268282] ? copyin+0xea/0x170
> [ 22.268990] kasan_report+0xd3/0x150
> [ 22.269551] ? quarantine_reduce+0x1/0x1a0
> [ 22.270177] ? copyin+0xea/0x170
> [ 22.270703] copyin+0xea/0x170
> [ 22.271202] _copy_from_iter_full+0x14f/0x4f0
> [ 22.271857] ? __kmalloc+0x1ad/0x2e0
> [ 22.272420] devkmsg_write+0xb9/0x1a0
> [ 22.272999] new_sync_write+0xd8/0x130
> [ 22.273579] vfs_write+0x174/0x2b0
> [ 22.274113] SyS_write+0x50/0xc0
> [ 22.274611] do_int80_syscall_32+0x7a/0x1b0
> [ 22.275216] entry_INT80_compat+0x2d/0x40
at a glance I don't see anything suspicious in devkmsg_write().
> [ 22.276103] Allocated by task 1:
> [ 22.276597] kasan_kmalloc+0x61/0xf0
> [ 22.277202] __kmalloc+0x1ad/0x2e0
> [ 22.277720] devkmsg_write+0x76/0x1a0
> [ 22.278268] new_sync_write+0xd8/0x130
> [ 22.278826] vfs_write+0x174/0x2b0
> [ 22.279342] SyS_write+0x50/0xc0
> [ 22.279840] do_int80_syscall_32+0x7a/0x1b0
> [ 22.280441] entry_INT80_compat+0x2d/0x40
devkmsg_write() does
buf = kmalloc(len+1, GFP_KERNEL);
...
kfree(buf);
kasan reports that this kfree() is actually happening in unpack_to_rootfs(),
before we do copy_from_iter_full().
> [ 22.281326] Freed by task 1:
> [ 22.281788] kasan_slab_free+0xac/0x180
> [ 22.282354] kfree+0x105/0x310
> [ 22.282837] unpack_to_rootfs+0x260/0x2a1
> [ 22.283420] populate_rootfs+0x5d/0x86
> [ 22.283977] do_one_initcall+0x3b/0x180
> [ 22.284544] do_basic_setup+0xb4/0xd0
> [ 22.285091] kernel_init_freeable+0x7b/0xed
> [ 22.285680] kernel_init+0xe/0x110
> [ 22.286171] ret_from_fork+0x25/0x30
unpack_to_rootfs() does
header_buf = kmalloc(110, GFP_KERNEL);
symlink_buf = kmalloc(PATH_MAX + N_ALIGN(PATH_MAX) + 1, GFP_KERNEL);
name_buf = kmalloc(N_ALIGN(PATH_MAX), GFP_KERNEL);
...
kfree(name_buf);
kfree(symlink_buf);
kfree(header_buf);
kasan reports that one of the pointers was allocated in devkmsg_write().
what am I missing?
-ss
