• Marek Szyprowski's avatar
    usb: gadget: u_ether: fix unsafe list iteration · b641ee14
    Marek Szyprowski authored
    [ Upstream commit c9287fa6 ]
    
    list_for_each_entry_safe() is not safe for deleting entries from the
    list if the spin lock, which protects it, is released and reacquired during
    the list iteration. Fix this issue by replacing this construction with
    a simple check if list is empty and removing the first entry in each
    iteration. This is almost equivalent to a revert of the commit mentioned in
    the Fixes: tag.
    
    This patch fixes following issue:
    --->8---
    Unable to handle kernel NULL pointer dereference at virtual address 00000104
    pgd = (ptrval)
    [00000104] *pgd=00000000
    Internal error: Oops: 817 [#1] PREEMPT SMP ARM
    Modules linked in:
    CPU: 1 PID: 84 Comm: kworker/1:1 Not tainted 4.20.0-rc2-next-20181114-00009-g8266b35ec404 #1061
    Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
    Workqueue: events eth_work
    PC is at rx_fill+0x60/0xac
    LR is at _raw_spin_lock_irqsave+0x50/0x5c
    pc : [<c065fee0>]    lr : [<c0a056b8>]    psr: 80000093
    sp : ee7fbee8  ip : 00000100  fp : 00000000
    r10: 006000c0  r9 : c10b0ab0  r8 : ee7eb5c0
    r7 : ee7eb614  r6 : ee7eb5ec  r5 : 000000dc  r4 : ee12ac00
    r3 : ee12ac24  r2 : 00000200  r1 : 60000013  r0 : ee7eb5ec
    Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
    Control: 10c5387d  Table: 6d5dc04a  DAC: 00000051
    Process kworker/1:1 (pid: 84, stack limit = 0x(ptrval))
    Stack: (0xee7fbee8 to 0xee7fc000)
    ...
    [<c065fee0>] (rx_fill) from [<c0143b7c>] (process_one_work+0x200/0x738)
    [<c0143b7c>] (process_one_work) from [<c0144118>] (worker_thread+0x2c/0x4c8)
    [<c0144118>] (worker_thread) from [<c014a8a4>] (kthread+0x128/0x164)
    [<c014a8a4>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
    Exception stack(0xee7fbfb0 to 0xee7fbff8)
    ...
    ---[ end trace 64480bc835eba7d6 ]---
    
    Fixes: fea14e68
    
     ("usb: gadget: u_ether: use better list accessors")
    Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
    Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
    Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
    b641ee14
u_ether.c 28.8 KB