Hi Ezra,
On 2025/2/12 15:27, Ezra Buehler wrote:
Hi Qi,
Thanks for the fix. I will test it as well as I can.
Thanks!
On Wed, Feb 12, 2025 at 7:41 AM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
When update_mmu_cache_range() is called by update_mmu_cache(), the vmf
parameter is NULL, which will cause a NULL pointer dereference issue in
adjust_pte():
Unable to handle kernel NULL pointer dereference at virtual address 00000030 when read
Hardware name: Atmel AT91SAM9
PC is at update_mmu_cache_range+0x1e0/0x278
LR is at pte_offset_map_rw_nolock+0x18/0x2c
Call trace:
update_mmu_cache_range from remove_migration_pte+0x29c/0x2ec
remove_migration_pte from rmap_walk_file+0xcc/0x130
rmap_walk_file from remove_migration_ptes+0x90/0xa4
remove_migration_ptes from migrate_pages_batch+0x6d4/0x858
migrate_pages_batch from migrate_pages+0x188/0x488
migrate_pages from compact_zone+0x56c/0x954
compact_zone from compact_node+0x90/0xf0
compact_node from kcompactd+0x1d4/0x204
kcompactd from kthread+0x120/0x12c
kthread from ret_from_fork+0x14/0x38
Exception stack(0xc0d8bfb0 to 0xc0d8bff8)
To fix it, do not rely on whether 'ptl' is equal to decide whether to hold
the pte lock, but decide it by whether CONFIG_SPLIT_PTE_PTLOCKS is
enabled. In addition, if two vmas map to the same PTE page, there is no
need to hold the pte lock again, otherwise a deadlock will occur. Just add
the need_lock parameter to let adjust_pte() know this information.
Reported-by: Ezra Buehler <ezra@xxxxxxxx>
Perhaps a detail but, maybe better use "Ezra Buehler
<ezra.buehler@xxxxxxxxxxxxxxxxxx>" here.
Got it. Will wait for your test results first.
Thanks,
Qi
Cheers,
Ezra.
