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Mehmet Fide
1232fd8cc2
fec_enet_alloc_rxq_buffers() leaves the loop as soon as page_pool_dev_alloc_pages() returns NULL and jumps to err_alloc, which calls fec_enet_free_buffers(). That helper walks the whole ring and hands every rx_skb_info[i].page to page_pool_put_full_page(), including the entries the allocation loop never reached. Those are still NULL, because the queue was allocated with kzalloc(), and page_pool_put_full_page() dereferences the page, so an open that runs out of memory oopses instead of returning -ENOMEM: Unable to handle kernel NULL pointer dereference at virtual address 00000014 when read Internal error: Oops: 5 [#1] SMP ARM CPU: 0 PID: 384 Comm: connmand Not tainted 6.18.43 #1 Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree) PC is at fec_enet_free_buffers+0xb0/0x2a8 Call trace: fec_enet_free_buffers from fec_enet_open+0x1e0/0x504 fec_enet_open from __dev_open+0x114/0x238 __dev_open from __dev_change_flags+0x190/0x208 __dev_change_flags from netif_change_flags+0x1c/0x58 netif_change_flags from dev_change_flags+0x44/0x74 dev_change_flags from devinet_ioctl+0x3a4/0x768 Seen on a Colibri VF50, 128 MiB of RAM, on the first ifup after boot. Skip the entries that hold no page, and clear the ones that do after releasing them, so that a later failed open cannot release the same page a second time. Mainline is not affected. Commita2ae70c0ef("net: fec: add fec_alloc_rxq_buffers_pp() to allocate buffers from page pool") replaced this loop with fec_free_rxq_buffers(), which skips and clears the empty entries. That commit is part of the XDP zero copy series and is not a stable candidate, so this is the equivalent minimal fix for 6.18.y. Fixes:95698ff617("net: fec: using page pool to manage RX buffers") Cc: stable@vger.kernel.org Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.