On Wed, 20 Apr 2016, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > If the caller, in this case efivarfs_callback(), only provides sufficent > room for the expanded utf8 and not enough to include the terminating NUL > byte, that NUL byte is skipped. When the caller then interprets it as a > string, it may then read from past its allocated memory: > > [ 170.605647] WARNING: kmemcheck: Caught 8-bit read from uninitialized memory (ffff8804079ae786) > [ 170.605677] 436f6e4f757400004c44322d35363062663538612d316530642d346437652d39 > [ 170.606037] i i i i i i u u u u u u u u u u u u u u u u u u u u u u u u u u > [ 170.606236] ^ > [ 170.606243] RIP: 0010:[<ffffffff813a251f>] [<ffffffff813a251f>] efivar_variable_is_removable+0xaf/0xf0 > [ 170.606346] RSP: 0018:ffff880408e73c20 EFLAGS: 00010206 > [ 170.606352] RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000000006 > [ 170.606359] RDX: 0000000000000000 RSI: 0000000000000074 RDI: ffff880408e73c30 > [ 170.606365] RBP: ffff880408e73c80 R08: 0000000000000006 R09: 000000000000008c > [ 170.606371] R10: 0000000000000006 R11: 0000000000000000 R12: ffffffff8166ed20 > [ 170.606378] R13: 11d293ca8be4df61 R14: ffffffff81773834 R15: ffff8804079ae780 > [ 170.606385] FS: 0000000000000000(0000) GS:ffff88041ca00000(0000) knlGS:0000000000000000 > [ 170.606392] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 170.606399] CR2: ffff880409cbe4c0 CR3: 00000004085fd000 CR4: 00000000001406f0 > [ 170.606405] [<ffffffff811eb938>] efivarfs_callback+0xf8/0x275 > [ 170.606418] [<ffffffff813a3368>] efivar_init+0x248/0x2e0 > [ 170.606440] [<ffffffff811eb6b4>] efivarfs_fill_super+0xb4/0xf0 > [ 170.606452] [<ffffffff811333e7>] mount_single+0x87/0xb0 > [ 170.606463] [<ffffffff811eb5f3>] efivarfs_mount+0x13/0x20 > [ 170.606475] [<ffffffff81133480>] mount_fs+0x10/0x90 > [ 170.606497] [<ffffffff8114c732>] vfs_kern_mount+0x62/0x100 > [ 170.606508] [<ffffffff8114ecb0>] do_mount+0x1e0/0xcd0 > [ 170.606519] [<ffffffff8114fa9f>] SyS_mount+0x8f/0xd0 > [ 170.606530] [<ffffffff81451d1f>] entry_SYSCALL_64_fastpath+0x17/0x93 > [ 170.606542] [<ffffffffffffffff>] 0xffffffffffffffff So I eyeballed the code a bit, and came across efivar_validate(), which calls variable_matches(), which definitely can access off by one beyond the passed in var_name on that call path. However I can't match that up with your backtrace, so may be another bug. BR, Jani. -- Jani Nikula, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
