jbd2: fix ERR_PTR dereference in jbd2__journal_start

If start_this_handle() failed handle will be initialized
to ERR_PTR() and can not be dereferenced.

paging request at fffffffffffffff6
IP: [<ffffffff813c073f>] jbd2__journal_start+0x18f/0x290
PGD 200e067 PUD 200f067 PMD 0
Oops: 0000 [#1] SMP
Modules linked in: cpufreq_ondemand acpi_cpufreq freq_table mperf coretemp kvm_intel kvm crc32c_intel ghash_clmulni_intel microcode sg xhci_hcd button sd_mod crc_t10dif aesni_intel ablk_helper cryptd lrw aes_x86_64 xts gf128mul ahci libahci pata_acpi ata_generic dm_mirror dm_region_hash dm_log dm_mod
CPU 0 journal commit I/O error

Pid: 2694, comm: fio Not tainted 3.8.0-rc3+ #79                  /DQ67SW
RIP: 0010:[<ffffffff813c073f>]  [<ffffffff813c073f>] jbd2__journal_start+0x18f/0x290
RSP: 0018:ffff880233b8ba58  EFLAGS: 00010292
RAX: 00000000ffffffe2 RBX: ffffffffffffffe2 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff82128f48
RBP: ffff880233b8ba98 R08: 0000000000000000 R09: ffff88021440a6e0

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index b7e2385..d6ee5ae 100644 (file)
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -382,7 +382,7 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, gfp_t gfp_mask,
        if (err < 0) {
                jbd2_free_handle(handle);
                current->journal_info = NULL;
-               handle = ERR_PTR(err);
+               return ERR_PTR(err);
        }
        handle->h_type = type;
        handle->h_line_no = line_no;