From: Petr Cvachoucek cvachoucek@gmail.com
commit 3fea4d9d160186617ff40490ae01f4f4f36b28ff upstream.
it seems freeing the write buffers in the error path of the ubifs_remount_rw() is wrong. It leads later to a kernel oops like this:
[10016.431274] UBIFS (ubi0:0): start fixing up free space [10090.810042] UBIFS (ubi0:0): free space fixup complete [10090.814623] UBIFS error (ubi0:0 pid 512): ubifs_remount_fs: cannot spawn "ubifs_bgt0_0", error -4 [10101.915108] UBIFS (ubi0:0): background thread "ubifs_bgt0_0" started, PID 517 [10105.275498] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030 [10105.284352] Mem abort info: [10105.287160] ESR = 0x96000006 [10105.290252] EC = 0x25: DABT (current EL), IL = 32 bits [10105.295592] SET = 0, FnV = 0 [10105.298652] EA = 0, S1PTW = 0 [10105.301848] Data abort info: [10105.304723] ISV = 0, ISS = 0x00000006 [10105.308573] CM = 0, WnR = 0 [10105.311564] user pgtable: 4k pages, 48-bit VAs, pgdp=00000000f03d1000 [10105.318034] [0000000000000030] pgd=00000000f6cee003, pud=00000000f4884003, pmd=0000000000000000 [10105.326783] Internal error: Oops: 96000006 [#1] PREEMPT SMP [10105.332355] Modules linked in: ath10k_pci ath10k_core ath mac80211 libarc4 cfg80211 nvme nvme_core cryptodev(O) [10105.342468] CPU: 3 PID: 518 Comm: touch Tainted: G O 5.4.3 #1 [10105.349517] Hardware name: HYPEX CPU (DT) [10105.353525] pstate: 40000005 (nZcv daif -PAN -UAO) [10105.358324] pc : atomic64_try_cmpxchg_acquire.constprop.22+0x8/0x34 [10105.364596] lr : mutex_lock+0x1c/0x34 [10105.368253] sp : ffff000075633aa0 [10105.371563] x29: ffff000075633aa0 x28: 0000000000000001 [10105.376874] x27: ffff000076fa80c8 x26: 0000000000000004 [10105.382185] x25: 0000000000000030 x24: 0000000000000000 [10105.387495] x23: 0000000000000000 x22: 0000000000000038 [10105.392807] x21: 000000000000000c x20: ffff000076fa80c8 [10105.398119] x19: ffff000076fa8000 x18: 0000000000000000 [10105.403429] x17: 0000000000000000 x16: 0000000000000000 [10105.408741] x15: 0000000000000000 x14: fefefefefefefeff [10105.414052] x13: 0000000000000000 x12: 0000000000000fe0 [10105.419364] x11: 0000000000000fe0 x10: ffff000076709020 [10105.424675] x9 : 0000000000000000 x8 : 00000000000000a0 [10105.429986] x7 : ffff000076fa80f4 x6 : 0000000000000030 [10105.435297] x5 : 0000000000000000 x4 : 0000000000000000 [10105.440609] x3 : 0000000000000000 x2 : ffff00006f276040 [10105.445920] x1 : ffff000075633ab8 x0 : 0000000000000030 [10105.451232] Call trace: [10105.453676] atomic64_try_cmpxchg_acquire.constprop.22+0x8/0x34 [10105.459600] ubifs_garbage_collect+0xb4/0x334 [10105.463956] ubifs_budget_space+0x398/0x458 [10105.468139] ubifs_create+0x50/0x180 [10105.471712] path_openat+0x6a0/0x9b0 [10105.475284] do_filp_open+0x34/0x7c [10105.478771] do_sys_open+0x78/0xe4 [10105.482170] __arm64_sys_openat+0x1c/0x24 [10105.486180] el0_svc_handler+0x84/0xc8 [10105.489928] el0_svc+0x8/0xc [10105.492808] Code: 52800013 17fffffb d2800003 f9800011 (c85ffc05) [10105.498903] ---[ end trace 46b721d93267a586 ]---
To reproduce the problem:
1. Filesystem initially mounted read-only, free space fixup flag set.
2. mount -o remount,rw <mountpoint>
3. it takes some time (free space fixup running) ... try to terminate running mount by CTRL-C ... does not respond, only after free space fixup is complete ... then "ubifs_remount_fs: cannot spawn "ubifs_bgt0_0", error -4"
4. mount -o remount,rw <mountpoint> ... now finished instantly (fixup already done).
5. Create file or just unmount the filesystem and we get the oops.
Cc: stable@vger.kernel.org Fixes: b50b9f408502 ("UBIFS: do not free write-buffers when in R/O mode") Signed-off-by: Petr Cvachoucek cvachoucek@gmail.com Signed-off-by: Richard Weinberger richard@nod.at Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ubifs/super.c | 1 - 1 file changed, 1 deletion(-)
--- a/fs/ubifs/super.c +++ b/fs/ubifs/super.c @@ -1835,7 +1835,6 @@ out: kthread_stop(c->bgt); c->bgt = NULL; } - free_wbufs(c); kfree(c->write_reserve_buf); c->write_reserve_buf = NULL; vfree(c->ileb_buf);