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authorPeter Hurley <peter@hurleysoftware.com>2015-11-27 14:18:39 -0500
committerDavid S. Miller <davem@davemloft.net>2015-12-01 15:17:42 -0500
commitee9159ddce14bc1dec9435ae4e3bd3153e783706 (patch)
treeb41f219cf9d4ce03d9f9ea0535d5b1807959c773 /drivers/net/wan
parent304d888b29cf96f1dd53511ee686499cd8cdf249 (diff)
downloadlinux-ee9159ddce14bc1dec9435ae4e3bd3153e783706.tar.bz2
wan/x25: Fix use-after-free in x25_asy_open_tty()
The N_X25 line discipline may access the previous line discipline's closed and already-freed private data on open [1]. The tty->disc_data field _never_ refers to valid data on entry to the line discipline's open() method. Rather, the ldisc is expected to initialize that field for its own use for the lifetime of the instance (ie. from open() to close() only). [1] [ 634.336761] ================================================================== [ 634.338226] BUG: KASAN: use-after-free in x25_asy_open_tty+0x13d/0x490 at addr ffff8800a743efd0 [ 634.339558] Read of size 4 by task syzkaller_execu/8981 [ 634.340359] ============================================================================= [ 634.341598] BUG kmalloc-512 (Not tainted): kasan: bad access detected ... [ 634.405018] Call Trace: [ 634.405277] dump_stack (lib/dump_stack.c:52) [ 634.405775] print_trailer (mm/slub.c:655) [ 634.406361] object_err (mm/slub.c:662) [ 634.406824] kasan_report_error (mm/kasan/report.c:138 mm/kasan/report.c:236) [ 634.409581] __asan_report_load4_noabort (mm/kasan/report.c:279) [ 634.411355] x25_asy_open_tty (drivers/net/wan/x25_asy.c:559 (discriminator 1)) [ 634.413997] tty_ldisc_open.isra.2 (drivers/tty/tty_ldisc.c:447) [ 634.414549] tty_set_ldisc (drivers/tty/tty_ldisc.c:567) [ 634.415057] tty_ioctl (drivers/tty/tty_io.c:2646 drivers/tty/tty_io.c:2879) [ 634.423524] do_vfs_ioctl (fs/ioctl.c:43 fs/ioctl.c:607) [ 634.427491] SyS_ioctl (fs/ioctl.c:622 fs/ioctl.c:613) [ 634.427945] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188) Reported-and-tested-by: Sasha Levin <sasha.levin@oracle.com> Cc: <stable@vger.kernel.org> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/wan')
-rw-r--r--drivers/net/wan/x25_asy.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/drivers/net/wan/x25_asy.c b/drivers/net/wan/x25_asy.c
index 5c47b011a9d7..cd39025d2abf 100644
--- a/drivers/net/wan/x25_asy.c
+++ b/drivers/net/wan/x25_asy.c
@@ -549,16 +549,12 @@ static void x25_asy_receive_buf(struct tty_struct *tty,
static int x25_asy_open_tty(struct tty_struct *tty)
{
- struct x25_asy *sl = tty->disc_data;
+ struct x25_asy *sl;
int err;
if (tty->ops->write == NULL)
return -EOPNOTSUPP;
- /* First make sure we're not already connected. */
- if (sl && sl->magic == X25_ASY_MAGIC)
- return -EEXIST;
-
/* OK. Find a free X.25 channel to use. */
sl = x25_asy_alloc();
if (sl == NULL)