Patch "spi: fix null pointer dereference within spi_sync" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    spi: fix null pointer dereference within spi_sync

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     spi-fix-null-pointer-dereference-within-spi_sync.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c9cba9ae1a12831e6af9cc6cde51f5f41aff504f
Author: Mans Rullgard <mans@xxxxxxxxx>
Date:   Tue Apr 30 19:27:05 2024 +0100

    spi: fix null pointer dereference within spi_sync
    
    [ Upstream commit 4756fa529b2f12b7cb8f21fe229b0f6f47190829 ]
    
    If spi_sync() is called with the non-empty queue and the same spi_message
    is then reused, the complete callback for the message remains set while
    the context is cleared, leading to a null pointer dereference when the
    callback is invoked from spi_finalize_current_message().
    
    With function inlining disabled, the call stack might look like this:
    
      _raw_spin_lock_irqsave from complete_with_flags+0x18/0x58
      complete_with_flags from spi_complete+0x8/0xc
      spi_complete from spi_finalize_current_message+0xec/0x184
      spi_finalize_current_message from spi_transfer_one_message+0x2a8/0x474
      spi_transfer_one_message from __spi_pump_transfer_message+0x104/0x230
      __spi_pump_transfer_message from __spi_transfer_message_noqueue+0x30/0xc4
      __spi_transfer_message_noqueue from __spi_sync+0x204/0x248
      __spi_sync from spi_sync+0x24/0x3c
      spi_sync from mcp251xfd_regmap_crc_read+0x124/0x28c [mcp251xfd]
      mcp251xfd_regmap_crc_read [mcp251xfd] from _regmap_raw_read+0xf8/0x154
      _regmap_raw_read from _regmap_bus_read+0x44/0x70
      _regmap_bus_read from _regmap_read+0x60/0xd8
      _regmap_read from regmap_read+0x3c/0x5c
      regmap_read from mcp251xfd_alloc_can_err_skb+0x1c/0x54 [mcp251xfd]
      mcp251xfd_alloc_can_err_skb [mcp251xfd] from mcp251xfd_irq+0x194/0xe70 [mcp251xfd]
      mcp251xfd_irq [mcp251xfd] from irq_thread_fn+0x1c/0x78
      irq_thread_fn from irq_thread+0x118/0x1f4
      irq_thread from kthread+0xd8/0xf4
      kthread from ret_from_fork+0x14/0x28
    
    Fix this by also setting message->complete to NULL when the transfer is
    complete.
    
    Fixes: ae7d2346dc89 ("spi: Don't use the message queue if possible in spi_sync")
    
    Signed-off-by: Mans Rullgard <mans@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20240430182705.13019-1-mans@xxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 46f1535487608..a7194f29c2007 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -4431,6 +4431,7 @@ static int __spi_sync(struct spi_device *spi, struct spi_message *message)
 		wait_for_completion(&done);
 		status = message->status;
 	}
+	message->complete = NULL;
 	message->context = NULL;
 
 	return status;