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CVE-2020-36557

A race condition in the Linux kernel before 5.6.2 between the VT_DISALLOCATE ioctl and closing/opening of ttys could lead to a use-after-free.

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#ios#mac#linux#js#git#intel#bios#auth#wifi

commit 9fbe5c87eaa9b72db08425c52c373eb5f6537a0a Author: Greg Kroah-Hartman Date: Thu Apr 2 08:02:32 2020 +0200 Linux 5.6.2 commit cea1c66b816e4f13ad7609cd0082e8f1ff98de0f Author: Georg Müller Date: Mon Feb 3 21:11:06 2020 +0100 platform/x86: pmc_atom: Add Lex 2I385SW to critclk_systems DMI table commit 95b31e35239e5e1689e3d965d692a313c71bd8ab upstream. The Lex 2I385SW board has two Intel I211 ethernet controllers. Without this patch, only the first port is usable. The second port fails to start with the following message: igb: probe of 0000:02:00.0 failed with error -2 Fixes: 648e921888ad (“clk: x86: Stop marking clocks as CLK_IS_CRITICAL”) Tested-by: Georg Müller Signed-off-by: Georg Müller Reviewed-by: Hans de Goede Signed-off-by: Andy Shevchenko Signed-off-by: Greg Kroah-Hartman commit 4d8b01733206b8016f6f5c853fdf02ec07f8e25c Author: Eric Biggers Date: Sat Mar 21 20:43:05 2020 -0700 vt: vt_ioctl: fix use-after-free in vt_in_use() commit 7cf64b18b0b96e751178b8d0505d8466ff5a448f upstream. vt_in_use() dereferences console_driver->ttys[i] without proper locking. This is broken because the tty can be closed and freed concurrently. We could fix this by using ‘READ_ONCE(console_driver->ttys[i]) != NULL’ and skipping the check of tty_struct::count. But, looking at console_driver->ttys[i] isn’t really appropriate anyway because even if it is NULL the tty can still be in the process of being closed. Instead, fix it by making vt_in_use() require console_lock() and check whether the vt is allocated and has port refcount > 1. This works since following the patch “vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console” the port refcount is incremented while the vt is open. Reproducer (very unreliable, but it worked for me after a few minutes): #include #include int main() { int fd, nproc; struct vt_stat state; char ttyname[16]; fd = open("/dev/tty10", O_RDONLY); for (nproc = 1; nproc < 8; nproc *= 2) fork(); for (;;) { sprintf(ttyname, "/dev/tty%d", rand() % 8); close(open(ttyname, O_RDONLY)); ioctl(fd, VT_GETSTATE, &state); } } KASAN report: BUG: KASAN: use-after-free in vt_in_use drivers/tty/vt/vt_ioctl.c:48 [inline] BUG: KASAN: use-after-free in vt_ioctl+0x1ad3/0x1d70 drivers/tty/vt/vt_ioctl.c:657 Read of size 4 at addr ffff888065722468 by task syz-vt2/132 CPU: 0 PID: 132 Comm: syz-vt2 Not tainted 5.6.0-rc5-00130-g089b6d3654916 #13 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20191223_100556-anatol 04/01/2014 Call Trace: […] vt_in_use drivers/tty/vt/vt_ioctl.c:48 [inline] vt_ioctl+0x1ad3/0x1d70 drivers/tty/vt/vt_ioctl.c:657 tty_ioctl+0x9db/0x11b0 drivers/tty/tty_io.c:2660 […] Allocated by task 136: […] kzalloc include/linux/slab.h:669 [inline] alloc_tty_struct+0x96/0x8a0 drivers/tty/tty_io.c:2982 tty_init_dev+0x23/0x350 drivers/tty/tty_io.c:1334 tty_open_by_driver drivers/tty/tty_io.c:1987 [inline] tty_open+0x3ca/0xb30 drivers/tty/tty_io.c:2035 […] Freed by task 41: […] kfree+0xbf/0x200 mm/slab.c:3757 free_tty_struct+0x8d/0xb0 drivers/tty/tty_io.c:177 release_one_tty+0x22d/0x2f0 drivers/tty/tty_io.c:1468 process_one_work+0x7f1/0x14b0 kernel/workqueue.c:2264 worker_thread+0x8b/0xc80 kernel/workqueue.c:2410 […] Fixes: 4001d7b7fc27 (“vt: push down the tty lock so we can see what is left to tackle”) Cc: # v3.4+ Acked-by: Jiri Slaby Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman commit 903f879e510838969d93506eea1a498fc9928c51 Author: Eric Biggers Date: Sat Mar 21 20:43:04 2020 -0700 vt: vt_ioctl: fix VT_DISALLOCATE freeing in-use virtual console commit ca4463bf8438b403596edd0ec961ca0d4fbe0220 upstream. The VT_DISALLOCATE ioctl can free a virtual console while tty_release() is still running, causing a use-after-free in con_shutdown(). This occurs because VT_DISALLOCATE considers a virtual console’s ‘struct vc_data’ to be unused as soon as the corresponding tty’s refcount hits 0. But actually it may be still being closed. Fix this by making vc_data be reference-counted via the embedded 'struct tty_port’. A newly allocated virtual console has refcount 1. Opening it for the first time increments the refcount to 2. Closing it for the last time decrements the refcount (in tty_operations::cleanup() so that it happens late enough), as does VT_DISALLOCATE. Reproducer: #include #include #include #include int main() { if (fork()) { for (;;) close(open("/dev/tty5", O_RDWR)); } else { int fd = open("/dev/tty10", O_RDWR); for (;;) ioctl(fd, VT_DISALLOCATE, 5); } } KASAN report: BUG: KASAN: use-after-free in con_shutdown+0x76/0x80 drivers/tty/vt/vt.c:3278 Write of size 8 at addr ffff88806a4ec108 by task syz_vt/129 CPU: 0 PID: 129 Comm: syz_vt Not tainted 5.6.0-rc2 #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20191223_100556-anatol 04/01/2014 Call Trace: […] con_shutdown+0x76/0x80 drivers/tty/vt/vt.c:3278 release_tty+0xa8/0x410 drivers/tty/tty_io.c:1514 tty_release_struct+0x34/0x50 drivers/tty/tty_io.c:1629 tty_release+0x984/0xed0 drivers/tty/tty_io.c:1789 […] Allocated by task 129: […] kzalloc include/linux/slab.h:669 [inline] vc_allocate drivers/tty/vt/vt.c:1085 [inline] vc_allocate+0x1ac/0x680 drivers/tty/vt/vt.c:1066 con_install+0x4d/0x3f0 drivers/tty/vt/vt.c:3229 tty_driver_install_tty drivers/tty/tty_io.c:1228 [inline] tty_init_dev+0x94/0x350 drivers/tty/tty_io.c:1341 tty_open_by_driver drivers/tty/tty_io.c:1987 [inline] tty_open+0x3ca/0xb30 drivers/tty/tty_io.c:2035 […] Freed by task 130: […] kfree+0xbf/0x1e0 mm/slab.c:3757 vt_disallocate drivers/tty/vt/vt_ioctl.c:300 [inline] vt_ioctl+0x16dc/0x1e30 drivers/tty/vt/vt_ioctl.c:818 tty_ioctl+0x9db/0x11b0 drivers/tty/tty_io.c:2660 […] Fixes: 4001d7b7fc27 (“vt: push down the tty lock so we can see what is left to tackle”) Cc: # v3.4+ Reported-by: [email protected] Acked-by: Jiri Slaby Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman commit 4e1c0484b7f84f55713b1eb1faf641ae49496bb1 Author: Eric Biggers Date: Mon Feb 24 00:03:26 2020 -0800 vt: vt_ioctl: remove unnecessary console allocation checks commit 1aa6e058dd6cd04471b1f21298270014daf48ac9 upstream. The vc_cons_allocated() checks in vt_ioctl() and vt_compat_ioctl() are unnecessary because they can only be reached by calling ioctl() on an open tty, which implies the corresponding virtual console is allocated. And even if the virtual console *could* be freed concurrently, then these checks would be broken since they aren’t done under console_lock, and the vc_data is dereferenced before them anyway. So, remove these unneeded checks to avoid confusion. Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman commit e50d4c4fecccef226a86e2a6be20ad376138e9ec Author: Jiri Slaby Date: Wed Feb 19 08:39:48 2020 +0100 vt: switch vt_dont_switch to bool commit f400991bf872debffb01c46da882dc97d7e3248e upstream. vt_dont_switch is pure boolean, no need for whole char. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman commit 270db0384de5867ca046c09418f129f5f78072f5 Author: Jiri Slaby Date: Wed Feb 19 08:39:44 2020 +0100 vt: ioctl, switch VT_IS_IN_USE and VT_BUSY to inlines commit e587e8f17433ddb26954f0edf5b2f95c42155ae9 upstream. These two were macros. Switch them to static inlines, so that it’s more understandable what they are doing. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman commit 3f0e2212be7c46a4a43df30c1dc4618e28ad94f9 Author: Jiri Slaby Date: Wed Feb 19 08:39:43 2020 +0100 vt: selection, introduce vc_is_sel commit dce05aa6eec977f1472abed95ccd71276b9a3864 upstream. Avoid global variables (namely sel_cons) by introducing vc_is_sel. It checks whether the parameter is the current selection console. This will help putting sel_cons to a struct later. Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman commit aab76df91483a8803a001c3f5e25b0a8d43f8151 Author: Lanqing Liu Date: Mon Mar 16 11:13:33 2020 +0800 serial: sprd: Fix a dereference warning commit efc176929a3505a30c3993ddd393b40893649bd2 upstream. We should validate if the ‘sup’ is NULL or not before freeing DMA memory, to fix below warning. "drivers/tty/serial/sprd_serial.c:1141 sprd_remove() error: we previously assumed ‘sup’ could be null (see line 1132)" Fixes: f4487db58eb7 (“serial: sprd: Add DMA mode support”) Reported-by: Dan Carpenter Signed-off-by: Lanqing Liu Cc: stable Link: https://lore.kernel.org/r/e2bd92691538e95b04a2c2a728f3292e1617018f.1584325957.git.liuhhome@gmail.com Signed-off-by: Greg Kroah-Hartman commit 7908d2658f92b5164d715959d51ebb88f4ad891b Author: Johannes Berg Date: Sun Mar 29 22:50:06 2020 +0200 mac80211: fix authentication with iwlwifi/mvm commit be8c827f50a0bcd56361b31ada11dc0a3c2fd240 upstream. The original patch didn’t copy the ieee80211_is_data() condition because on most drivers the management frames don’t go through this path. However, they do on iwlwifi/mvm, so we do need to keep the condition here. Cc: [email protected] Fixes: ce2e1ca70307 (“mac80211: Check port authorization in the ieee80211_tx_dequeue() case”) Signed-off-by: Johannes Berg Signed-off-by: David S. Miller Cc: Woody Suwalski Signed-off-by: Greg Kroah-Hartman commit cb7cd49c9c281cf00fa38a53c2e6ccf708318b87 Author: Daniel Borkmann Date: Fri Jan 24 14:21:14 2020 +0000 bpf: update jmp32 test cases to fix range bound deduction [ no upstream commit ] Since commit f2d67fec0b43 (“bpf: Undo incorrect __reg_bound_offset32 handling”) has been backported to stable, we also need to update related test cases that started to (expectedly) fail on stable. Given the functionality has been reverted we need to move the result to REJECT. Reported-by: Naresh Kamboju Signed-off-by: Daniel Borkmann Signed-off-by: Greg Kroah-Hartman

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