3.16.66-rc1 review patch. If anyone has any objections, please let me know.
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From: "Eric W. Biederman" ebiederm@xmission.com
commit 2236d4d39035b9839944603ec4b65ce71180a9ea upstream.
The 0day kernel test build report reported an oops:
IP: put_pid+0x22/0x5c PGD 19efa067 P4D 19efa067 PUD 0 Oops: 0000 [#1] CPU: 0 PID: 727 Comm: trinity Not tainted 4.16.0-rc2-00010-g98f929b #1 RIP: 0010:put_pid+0x22/0x5c RSP: 0018:ffff986719f73e48 EFLAGS: 00010202 RAX: 00000006d765f710 RBX: ffff98671a4fa4d0 RCX: ffff986719f73d40 RDX: 000000006f6e6125 RSI: 0000000000000000 RDI: ffffffffa01e6d21 RBP: ffffffffa0955fe0 R08: 0000000000000020 R09: 0000000000000000 R10: 0000000000000078 R11: ffff986719f73e76 R12: 0000000000001000 R13: 00000000ffffffea R14: 0000000054000fb0 R15: 0000000000000000 FS: 00000000028c2880(0000) GS:ffffffffa06ad000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000677846439 CR3: 0000000019fc1005 CR4: 00000000000606b0 Call Trace: ? ipc_update_pid+0x36/0x3e ? newseg+0x34c/0x3a6 ? ipcget+0x5d/0x528 ? entry_SYSCALL_64_after_hwframe+0x52/0xb7 ? SyS_shmget+0x5a/0x84 ? do_syscall_64+0x194/0x1b3 ? entry_SYSCALL_64_after_hwframe+0x42/0xb7 Code: ff 05 e7 20 9b 03 58 c9 c3 48 ff 05 85 21 9b 03 48 85 ff 74 4f 8b 47 04 8b 17 48 ff 05 7c 21 9b 03 48 83 c0 03 48 c1 e0 04 ff ca <48> 8b 44 07 08 74 1f 48 ff 05 6c 21 9b 03 ff 0f 0f 94 c2 48 ff RIP: put_pid+0x22/0x5c RSP: ffff986719f73e48 CR2: 0000000677846439 ---[ end trace ab8c5cb4389d37c5 ]--- Kernel panic - not syncing: Fatal exception
In newseg when changing shm_cprid and shm_lprid from pid_t to struct pid* I misread the kvmalloc as kvzalloc and thought shp was initialized to 0. As that is not the case it is not safe to for the error handling to address shm_cprid and shm_lprid before they are initialized.
Therefore move the cleanup of shm_cprid and shm_lprid from the no_file error cleanup path to the no_id error cleanup path. Ensuring that an early error exit won't cause the oops above.
Reported-by: kernel test robot fengguang.wu@intel.com Reviewed-by: Nagarathnam Muthusamy nagarathnam.muthusamy@oracle.com Signed-off-by: Eric W. Biederman ebiederm@xmission.com [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- ipc/shm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/ipc/shm.c +++ b/ipc/shm.c @@ -620,12 +620,12 @@ static int newseg(struct ipc_namespace * return error;
no_id: + ipc_update_pid(&shp->shm_cprid, NULL); + ipc_update_pid(&shp->shm_lprid, NULL); if (is_file_hugepages(file) && shp->mlock_user) user_shm_unlock(size, shp->mlock_user); fput(file); no_file: - ipc_update_pid(&shp->shm_cprid, NULL); - ipc_update_pid(&shp->shm_lprid, NULL); ipc_rcu_putref(shp, shm_rcu_free); return error; }