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authorCong Wang <xiyou.wangcong@gmail.com>2017-08-10 15:24:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-08-10 15:54:07 -0700
commitd041353dc98a6339182cd6f628b4c8f111278cb3 (patch)
tree7eeb136da7771ff91e2b8ee04d1dae6e5ef34841
parentaf54aed94bf3a1cf0b847bbbf00f9a58e278b338 (diff)
downloadlinux-stericsson-d041353dc98a6339182cd6f628b4c8f111278cb3.tar.gz
mm: fix list corruptions on shmem shrinklist
We saw many list corruption warnings on shmem shrinklist: WARNING: CPU: 18 PID: 177 at lib/list_debug.c:59 __list_del_entry+0x9e/0xc0 list_del corruption. prev->next should be ffff9ae5694b82d8, but was ffff9ae5699ba960 Modules linked in: intel_rapl sb_edac edac_core x86_pkg_temp_thermal coretemp iTCO_wdt iTCO_vendor_support crct10dif_pclmul crc32_pclmul ghash_clmulni_intel raid0 dcdbas shpchp wmi hed i2c_i801 ioatdma lpc_ich i2c_smbus acpi_cpufreq tcp_diag inet_diag sch_fq_codel ipmi_si ipmi_devintf ipmi_msghandler igb ptp crc32c_intel pps_core i2c_algo_bit i2c_core dca ipv6 crc_ccitt CPU: 18 PID: 177 Comm: kswapd1 Not tainted 4.9.34-t3.el7.twitter.x86_64 #1 Hardware name: Dell Inc. PowerEdge C6220/0W6W6G, BIOS 2.2.3 11/07/2013 Call Trace: dump_stack+0x4d/0x66 __warn+0xcb/0xf0 warn_slowpath_fmt+0x4f/0x60 __list_del_entry+0x9e/0xc0 shmem_unused_huge_shrink+0xfa/0x2e0 shmem_unused_huge_scan+0x20/0x30 super_cache_scan+0x193/0x1a0 shrink_slab.part.41+0x1e3/0x3f0 shrink_slab+0x29/0x30 shrink_node+0xf9/0x2f0 kswapd+0x2d8/0x6c0 kthread+0xd7/0xf0 ret_from_fork+0x22/0x30 WARNING: CPU: 23 PID: 639 at lib/list_debug.c:33 __list_add+0x89/0xb0 list_add corruption. prev->next should be next (ffff9ae5699ba960), but was ffff9ae5694b82d8. (prev=ffff9ae5694b82d8). Modules linked in: intel_rapl sb_edac edac_core x86_pkg_temp_thermal coretemp iTCO_wdt iTCO_vendor_support crct10dif_pclmul crc32_pclmul ghash_clmulni_intel raid0 dcdbas shpchp wmi hed i2c_i801 ioatdma lpc_ich i2c_smbus acpi_cpufreq tcp_diag inet_diag sch_fq_codel ipmi_si ipmi_devintf ipmi_msghandler igb ptp crc32c_intel pps_core i2c_algo_bit i2c_core dca ipv6 crc_ccitt CPU: 23 PID: 639 Comm: systemd-udevd Tainted: G W 4.9.34-t3.el7.twitter.x86_64 #1 Hardware name: Dell Inc. PowerEdge C6220/0W6W6G, BIOS 2.2.3 11/07/2013 Call Trace: dump_stack+0x4d/0x66 __warn+0xcb/0xf0 warn_slowpath_fmt+0x4f/0x60 __list_add+0x89/0xb0 shmem_setattr+0x204/0x230 notify_change+0x2ef/0x440 do_truncate+0x5d/0x90 path_openat+0x331/0x1190 do_filp_open+0x7e/0xe0 do_sys_open+0x123/0x200 SyS_open+0x1e/0x20 do_syscall_64+0x61/0x170 entry_SYSCALL64_slow_path+0x25/0x25 The problem is that shmem_unused_huge_shrink() moves entries from the global sbinfo->shrinklist to its local lists and then releases the spinlock. However, a parallel shmem_setattr() could access one of these entries directly and add it back to the global shrinklist if it is removed, with the spinlock held. The logic itself looks solid since an entry could be either in a local list or the global list, otherwise it is removed from one of them by list_del_init(). So probably the race condition is that, one CPU is in the middle of INIT_LIST_HEAD() but the other CPU calls list_empty() which returns true too early then the following list_add_tail() sees a corrupted entry. list_empty_careful() is designed to fix this situation. [akpm@linux-foundation.org: add comments] Link: http://lkml.kernel.org/r/20170803054630.18775-1-xiyou.wangcong@gmail.com Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure") Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/shmem.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index b0aa6075d164..6540e5982444 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1022,7 +1022,11 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
*/
if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
spin_lock(&sbinfo->shrinklist_lock);
- if (list_empty(&info->shrinklist)) {
+ /*
+ * _careful to defend against unlocked access to
+ * ->shrink_list in shmem_unused_huge_shrink()
+ */
+ if (list_empty_careful(&info->shrinklist)) {
list_add_tail(&info->shrinklist,
&sbinfo->shrinklist);
sbinfo->shrinklist_len++;
@@ -1817,7 +1821,11 @@ alloc_nohuge: page = shmem_alloc_and_acct_page(gfp, info, sbinfo,
* to shrink under memory pressure.
*/
spin_lock(&sbinfo->shrinklist_lock);
- if (list_empty(&info->shrinklist)) {
+ /*
+ * _careful to defend against unlocked access to
+ * ->shrink_list in shmem_unused_huge_shrink()
+ */
+ if (list_empty_careful(&info->shrinklist)) {
list_add_tail(&info->shrinklist,
&sbinfo->shrinklist);
sbinfo->shrinklist_len++;