https://bugzilla.kernel.org/show_bug.cgi?id=30872 Summary: Calling kfree() for uninitialized pointer in ext4_mb_init_backend() Product: File System Version: 2.5 Kernel Version: 2.6.38-rc5 (ext4 subsystem tree) Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: ext4 AssignedTo: fs_ext4@xxxxxxxxxxxxxxxxxxxx ReportedBy: dame_eugene@xxxxxxx Regression: No Tested on ext4 module from git tree git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git, tip: b616844310a6c8a4ab405d3436bbb6e53cfd852f Arch: x86 At fs/ext4/mballoc.c:2389, memory is allocated for sbi->s_group_info array. The elements of this array (pointers themselves) seem to be initialized when ext4_mb_add_groupinfo() is called (line 2408). If ext4_mb_add_groupinfo() fails for some reason (e.g. if memory allocation at line 2296 fails), ext4_mb_init_backend() tries to call kfree() for each element in sbi->s_group_info array, including the ones that have not been initialized yet: fs/ext4/mballoc.c:2414: err_freebuddy: cachep = get_groupinfo_cache(sb->s_blocksize_bits); while (i-- > 0) kmem_cache_free(cachep, ext4_get_group_info(sb, i)); i = num_meta_group_infos; while (i-- > 0) kfree(sbi->s_group_info[i]); /* <= oops here */ iput(sbi->s_buddy_cache); 'num_meta_group_infos' seems to be the total number of the elements that should have been created. The problem showed up when I ran tests for ext4 from Linux Test Project (ext4-alloc-test, test #7, to be exact). 'num_meta_group_infos' was 12 on my system. The first 2 calls to ext4_mb_add_groupinfo() (ln 2408) succeeded but the 3rd one failed. kfree(sbi->s_group_info[11]) resulted in a kernel oops: -------------------------------------------------- [ 6349.953315] EXT4-fs: can't allocate buddy mem [ 6349.953587] BUG: unable to handle kernel paging request at f7853a00 [ 6349.953591] IP: [<c02f1273>] kfree+0x43/0xf0 [ 6349.953613] *pde = 00000000 [ 6349.953615] Oops: 0000 [#1] SMP [ 6349.953617] last sysfs file: /sys/devices/virtual/block/loop1/queue/rotational [ 6349.953623] Modules linked in: ext4 jbd2 crc16 kedr_controller kedr_fsim_indicator_kmalloc kedr_fsim_indicator_common kedr_fsim_vmm kedr_fsim_mem_util kedr_fsim_cmm kedr_fault_simulation kedr_trace kedr_base fuse snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device edd af_packet mperf loop dm_mod ppdev snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm parport_pc snd_timer parport snd sr_mod cdrom ac e1000 sg i2c_piix4 soundcore snd_page_alloc button pcspkr ohci_hcd ehci_hcd rtc_cmos rtc_core rtc_lib usbcore sd_mod fan processor ata_generic ata_piix thermal thermal_sys hwmon ahci libahci libata scsi_mod [last unloaded: kedr_base] [ 6349.953655] [ 6349.953657] Pid: 8379, comm: mount Not tainted 2.6.38-rc5-testbox-ext4+ #1 innotek GmbH VirtualBox [ 6349.953664] EIP: 0060:[<c02f1273>] EFLAGS: 00010086 CPU: 0 [ 6349.953666] EIP is at kfree+0x43/0xf0 [ 6349.953667] EAX: f7853a00 EBX: 02b50001 ECX: 00000000 EDX: 000000bb [ 6349.953669] ESI: f8a15391 EDI: 00000202 EBP: e7e03d70 ESP: e7e03d60 [ 6349.953670] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 [ 6349.953672] Process mount (pid: 8379, ti=e7e02000 task=f66bed30 task.ti=e7e02000) [ 6349.953674] Stack: [ 6349.953675] eea9cae8 02b50001 f446f400 f446f400 e7e03d8c f8a15391 f8f01609 00000002 [ 6349.953679] 00032609 02b50001 0000000a e7e03dbc f8f01609 00020000 00000000 f47ce1c0 [ 6349.953683] f446f400 f446f400 0000000c f446f400 f446f400 e4866bf0 f446f400 e7e03e98 [ 6349.953687] Call Trace: [ 6349.953691] [<f8a15391>] repl_kfree+0x51/0xa0 [kedr_fsim_cmm] [ 6349.953709] [<f8f01609>] ext4_mb_init+0x2a9/0x4b0 [ext4] [ 6349.953716] [<f8ef1b22>] ext4_fill_super+0x2602/0x2ae0 [ext4] [ 6349.953726] [<c02fd920>] mount_bdev+0x170/0x1b0 [ 6349.953732] [<f8ee706a>] ext4_mount+0x1a/0x20 [ext4] [ 6349.953741] [<c02fd0f0>] vfs_kern_mount+0x70/0x230 [ 6349.953753] [<c02fd309>] do_kern_mount+0x39/0xd0 [ 6349.953755] [<c0314d72>] do_mount+0x432/0x6c0 [ 6349.953768] [<c0315326>] sys_mount+0x66/0xa0 [ 6349.953771] [<c0202ddc>] sysenter_do_call+0x12/0x28 [ 6349.953772] Code: 7d fc 85 c9 75 73 83 fb 10 76 61 9c 58 8d 74 26 00 89 c7 fa 90 8d 74 26 00 8d 83 00 00 00 40 c1 e8 0c c1 e0 05 03 05 64 ff 86 c0 <8b> 10 80 e6 80 0f 85 8b 00 00 00 8b 10 80 e6 80 75 7c 8b 10 81 [ 6349.953796] EIP: [<c02f1273>] kfree+0x43/0xf0 SS:ESP 0068:e7e03d60 [ 6349.953799] CR2: 00000000f7853a00 [ 6349.953801] ---[ end trace 8e09ff66f4f48163 ]--- -------------------------------------------------- If I understand correctly what happens in ext4_mb_init_backend(), zeroing sbi->s_group_info on allocation could fix the problem: fs/ext4/mballoc.c:2389: - sbi->s_group_info = kmalloc(array_size, GFP_KERNEL); + sbi->s_group_info = kzalloc(array_size, GFP_KERNEL); This issue was detected with the help of KEDR framework (http://kedr.berlios.de/). repl_kfree() that can be seen in the call stack above is a thin wrapper around kfree() that simply output its argument to a trace. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
