On Sat, Jan 11, 2025 at 10:15:20PM +0800, alvalan9@xxxxxxxxxxx wrote: > From: David Hildenbrand <david@xxxxxxxxxx> > > [ Upstream commit 091c1dd2d4df6edd1beebe0e5863d4034ade9572 ] > > We currently assume that there is at least one VMA in a MM, which isn't > true. > > So we might end up having find_vma() return NULL, to then de-reference > NULL. So properly handle find_vma() returning NULL. > > This fixes the report: > > Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] > CPU: 1 UID: 0 PID: 6021 Comm: syz-executor284 Not tainted 6.12.0-rc7-syzkaller-00187-gf868cd251776 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024 > RIP: 0010:migrate_to_node mm/mempolicy.c:1090 [inline] > RIP: 0010:do_migrate_pages+0x403/0x6f0 mm/mempolicy.c:1194 > Code: ... > RSP: 0018:ffffc9000375fd08 EFLAGS: 00010246 > RAX: 0000000000000000 RBX: ffffc9000375fd78 RCX: 0000000000000000 > RDX: ffff88807e171300 RSI: dffffc0000000000 RDI: ffff88803390c044 > RBP: ffff88807e171428 R08: 0000000000000014 R09: fffffbfff2039ef1 > R10: ffffffff901cf78f R11: 0000000000000000 R12: 0000000000000003 > R13: ffffc9000375fe90 R14: ffffc9000375fe98 R15: ffffc9000375fdf8 > FS: 00005555919e1380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00005555919e1ca8 CR3: 000000007f12a000 CR4: 00000000003526f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > kernel_migrate_pages+0x5b2/0x750 mm/mempolicy.c:1709 > __do_sys_migrate_pages mm/mempolicy.c:1727 [inline] > __se_sys_migrate_pages mm/mempolicy.c:1723 [inline] > __x64_sys_migrate_pages+0x96/0x100 mm/mempolicy.c:1723 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > > [akpm@xxxxxxxxxxxxxxxxxxxx: add unlikely()] > Link: https://lkml.kernel.org/r/20241120201151.9518-1-david@xxxxxxxxxx > Fixes: 39743889aaf7 ("[PATCH] Swap Migration V5: sys_migrate_pages interface") > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > Reported-by: syzbot+3511625422f7aa637f0d@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/lkml/673d2696.050a0220.3c9d61.012f.GAE@xxxxxxxxxx/T/ > Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > Reviewed-by: Christoph Lameter <cl@xxxxxxxxx> > Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > [ Remove mmap_read_unlock() because mmap_read_lock() is not called before find_vma() ] > Signed-off-by: Alva Lan <alvalan9@xxxxxxxxxxx> > --- > mm/mempolicy.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 399d8cb48813..d67dd0f503fa 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1068,6 +1068,9 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest, > * space range and MPOL_MF_DISCONTIG_OK, this call can not fail. > */ > vma = find_vma(mm, 0); > + if (unlikely(!vma)) { > + return 0; > + } Please follow the proper kernel coding style when doing backports, you have {} here where not needed, AND you have trailing whitespace :( Also, I'd like for someone on the reviewed-by chain to review that this backport actually is ok before applying it (after you fix it up...) thanks, greg k-h
