From: Zhengjun Xing zhengjun.xing@linux.intel.com

Commit dde634057da7 ("xhci: Fix use-after-free in xhci debugfs") causes a null pointer dereference while fixing xhci-debugfs usage of ring pointers that were freed during hibernate.

The fix passed addresses to ring pointers instead, but forgot to do this change for the xhci_ring_trb_show function.

The address of the ring pointer passed to xhci-debugfs was of a temporary ring pointer "new_ring" instead of the actual ring "ring" pointer. The temporary new_ring pointer will be set to NULL later causing the NULL pointer dereference.

This issue was seen when reading xhci related files in debugfs:

cat /sys/kernel/debug/usb/xhci/*/devices/*/ep*/trbs

[ 184.604861] BUG: unable to handle kernel NULL pointer dereference at (null) [ 184.613776] IP: xhci_ring_trb_show+0x3a/0x890 [ 184.618733] PGD 264193067 P4D 264193067 PUD 263238067 PMD 0 [ 184.625184] Oops: 0000 [#1] SMP [ 184.726410] RIP: 0010:xhci_ring_trb_show+0x3a/0x890 [ 184.731944] RSP: 0018:ffffba8243c0fd90 EFLAGS: 00010246 [ 184.737880] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000000295d6 [ 184.746020] RDX: 00000000000295d5 RSI: 0000000000000001 RDI: ffff971a6418d400 [ 184.754121] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 184.762222] R10: ffff971a64c98a80 R11: ffff971a62a00e40 R12: ffff971a62a85500 [ 184.770325] R13: 0000000000020000 R14: ffff971a6418d400 R15: ffff971a6418d400 [ 184.778448] FS: 00007fe725a79700(0000) GS:ffff971a6ec00000(0000) knlGS:0000000000000000 [ 184.787644] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 184.794168] CR2: 0000000000000000 CR3: 000000025f365005 CR4: 00000000003606f0 [ 184.802318] Call Trace: [ 184.805094] ? seq_read+0x281/0x3b0 [ 184.809068] seq_read+0xeb/0x3b0 [ 184.812735] full_proxy_read+0x4d/0x70 [ 184.817007] __vfs_read+0x23/0x120 [ 184.820870] vfs_read+0x91/0x130 [ 184.824538] SyS_read+0x42/0x90 [ 184.828106] entry_SYSCALL_64_fastpath+0x1a/0x7d

Fixes: dde634057da7 ("xhci: Fix use-after-free in xhci debugfs") Cc: stable@vger.kernel.org # v4.15 Signed-off-by: Zhengjun Xing zhengjun.xing@linux.intel.com Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com --- drivers/usb/host/xhci-debugfs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci-debugfs.c b/drivers/usb/host/xhci-debugfs.c index e26e685..5851052 100644 --- a/drivers/usb/host/xhci-debugfs.c +++ b/drivers/usb/host/xhci-debugfs.c @@ -211,7 +211,7 @@ static void xhci_ring_dump_segment(struct seq_file *s, static int xhci_ring_trb_show(struct seq_file *s, void *unused) { int i; - struct xhci_ring *ring = s->private; + struct xhci_ring *ring = *(struct xhci_ring **)s->private; struct xhci_segment *seg = ring->first_seg;

for (i = 0; i < ring->num_segs; i++) { @@ -387,7 +387,7 @@ void xhci_debugfs_create_endpoint(struct xhci_hcd *xhci,

snprintf(epriv->name, sizeof(epriv->name), "ep%02d", ep_index); epriv->root = xhci_debugfs_create_ring_dir(xhci, - &dev->eps[ep_index].new_ring, + &dev->eps[ep_index].ring, epriv->name, spriv->root); spriv->eps[ep_index] = epriv;