[PATCH] xhci:Fix NULL pointer in xhci debugfs
From: Zhengjun Xing
Date: Thu Jan 18 2018 - 21:13:19 EST
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")
Signed-off-by: Zhengjun Xing <zhengjun.xing@xxxxxxxxxxxxxxx>
---
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 e26e685d8a57..5851052d4668 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;
--
2.11.0