mainline inclusion from mainline-v6.9-rc1 commit 5aa598a72eafcf05239519646ec88638c8894dba category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I9S4Z4 CVE: NA
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The rounddown_pow_of_two(0) is undefined, so val = 0 is not allowed in the fault_around_bytes_set(), and leads to shift-out-of-bounds,
UBSAN: shift-out-of-bounds in include/linux/log2.h:67:13 shift exponent 4294967295 is too large for 64-bit type 'long unsigned int' CPU: 7 PID: 107 Comm: sh Not tainted 6.8.0-rc6-next-20240301 #294 Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: dump_backtrace+0x94/0xec show_stack+0x18/0x24 dump_stack_lvl+0x78/0x90 dump_stack+0x18/0x24 ubsan_epilogue+0x10/0x44 __ubsan_handle_shift_out_of_bounds+0x98/0x134 fault_around_bytes_set+0xa4/0xb0 simple_attr_write_xsigned.isra.0+0xe4/0x1ac simple_attr_write+0x18/0x24 debugfs_attr_write+0x4c/0x98 vfs_write+0xd0/0x4b0 ksys_write+0x6c/0xfc __arm64_sys_write+0x1c/0x28 invoke_syscall+0x44/0x104 el0_svc_common.constprop.0+0x40/0xe0 do_el0_svc+0x1c/0x28 el0_svc+0x34/0xdc el0t_64_sync_handler+0xc0/0xc4 el0t_64_sync+0x190/0x194 ---[ end trace ]---
Fix it by setting the minimum val to PAGE_SIZE.
Link: https://lkml.kernel.org/r/20240302064312.2358924-1-wangkefeng.wang@huawei.co... Fixes: 53d36a56d8c4 ("mm: prefer fault_around_pages to fault_around_bytes") Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com Reported-by: Yue Sun samsun1006219@gmail.com Closes: https://lore.kernel.org/all/CAEkJfYPim6DQqW1GqCiHLdh2-eweqk1fGyXqs3JM+8e1qGg... Reviewed-by: Lorenzo Stoakes lstoakes@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org (cherry picked from commit 5aa598a72eafcf05239519646ec88638c8894dba) Signed-off-by: Kefeng Wang wangkefeng.wang@huawei.com --- mm/memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c index fa4d1b499511..5a0e935712d4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4807,7 +4807,8 @@ static int fault_around_bytes_set(void *data, u64 val) * The minimum value is 1 page, however this results in no fault-around * at all. See should_fault_around(). */ - fault_around_pages = max(rounddown_pow_of_two(val) >> PAGE_SHIFT, 1UL); + val = max(val, PAGE_SIZE); + fault_around_pages = rounddown_pow_of_two(val) >> PAGE_SHIFT;
return 0; }