mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/
synced 2026-10-24 19:10:26 +00:00
15b8a5b4cd
commit95920c2ed0upstream. Helge reported that the introduction of PP_MAGIC_MASK let to crashes on boot on his 32-bit parisc machine. The cause of this is the mask is set too wide, so the page_pool_page_is_pp() incurs false positives which crashes the machine. Just disabling the check in page_pool_is_pp() will lead to the page_pool code itself malfunctioning; so instead of doing this, this patch changes the define for PP_DMA_INDEX_BITS to avoid mistaking arbitrary kernel pointers for page_pool-tagged pages. The fix relies on the kernel pointers that alias with the pp_magic field always being above PAGE_OFFSET. With this assumption, we can use the lowest bit of the value of PAGE_OFFSET as the upper bound of the PP_DMA_INDEX_MASK, which should avoid the false positives. Because we cannot rely on PAGE_OFFSET always being a compile-time constant, nor on it always being >0, we fall back to disabling the dma_index storage when there are not enough bits available. This leaves us in the situation we were in before the patch in the Fixes tag, but only on a subset of architecture configurations. This seems to be the best we can do until the transition to page types in complete for page_pool pages. v2: - Make sure there's at least 8 bits available and that the PAGE_OFFSET bit calculation doesn't wrap Link: https://lore.kernel.org/all/aMNJMFa5fDalFmtn@p100/ Fixes:ee62ce7a1d("page_pool: Track DMA-mapped pages and unmap them when destroying the pool") Cc: stable@vger.kernel.org # 6.15+ Tested-by: Helge Deller <deller@gmx.de> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Reviewed-by: Mina Almasry <almasrymina@google.com> Tested-by: Helge Deller <deller@gmx.de> Link: https://patch.msgid.link/20250930114331.675412-1-toke@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
4368 lines
131 KiB
4368 lines
131 KiB