On 2011.11.22 at 10:38 +0100, Eric Dumazet wrote: > Le mardi 22 novembre 2011 à 09:45 +0100, Markus Trippelsdorf a écrit : > > > I sometimes see the following pattern. Is this a false positive? > > > > > > ============================================================================= > > BUG anon_vma: Redzone overwritten > > ----------------------------------------------------------------------------- > > > > INFO: 0xffff88020f347c80-0xffff88020f347c87. First byte 0xbb instead of 0xcc > > INFO: Allocated in anon_vma_fork+0x51/0x140 age=1 cpu=2 pid=1826 > > __slab_alloc.constprop.70+0x1ac/0x1e8 > > kmem_cache_alloc+0x12e/0x160 > > anon_vma_fork+0x51/0x140 > > dup_mm+0x1f2/0x4a0 > > copy_process+0xd10/0xf70 > > do_fork+0x100/0x2b0 > > sys_clone+0x23/0x30 > > stub_clone+0x13/0x20 > > INFO: Freed in __put_anon_vma+0x54/0xa0 age=0 cpu=1 pid=1827 > > __slab_free+0x33/0x2d0 > > kmem_cache_free+0x10e/0x120 > > __put_anon_vma+0x54/0xa0 > > unlink_anon_vmas+0x12f/0x1c0 > > free_pgtables+0x83/0xe0 > > exit_mmap+0xee/0x140 > > mmput+0x43/0xf0 > > flush_old_exec+0x33f/0x630 > > load_elf_binary+0x340/0x1960 > > search_binary_handler+0x8f/0x180 > > do_execve+0x2d3/0x370 > > sys_execve+0x42/0x70 > > stub_execve+0x6c/0xc0 > > INFO: Slab 0xffffea00083cd1c0 objects=10 used=9 fp=0xffff88020f347ab8 flags=0x4000000000000081 > > INFO: Object 0xffff88020f347c40 @offset=3136 fp=0xffff88020f347ab8 > > > > Bytes b4 ffff88020f347c30: 39 b6 fb ff 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a 9.......ZZZZZZZZ > > Object ffff88020f347c40: 30 c9 9b 0d 02 88 ff ff 01 00 00 00 00 00 5a 5a 0.............ZZ > > Object ffff88020f347c50: 50 7c 34 0f 02 88 ff ff 50 7c 34 0f 02 88 ff ff P|4.....P|4..... > > Object ffff88020f347c60: 00 00 00 00 00 00 00 00 00 00 00 00 5a 5a 5a 5a ............ZZZZ > > Object ffff88020f347c70: 70 7c 34 0f 02 88 ff ff 70 7c 34 0f 02 88 ff ff p|4.....p|4..... > > Redzone ffff88020f347c80: bb bb bb bb bb bb bb bb ........ > > Padding ffff88020f347dc0: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ > > Pid: 1820, comm: slabinfo Not tainted 3.2.0-rc2-00369-gbbbc479-dirty #83 > > Call Trace: > > [<ffffffff81105df8>] ? print_section+0x38/0x40 > > [<ffffffff811062f3>] print_trailer+0xe3/0x150 > > [<ffffffff811064f0>] check_bytes_and_report+0xe0/0x100 > > [<ffffffff81107313>] check_object+0x183/0x240 > > [<ffffffff81107eb0>] validate_slab_slab+0x1c0/0x230 > > [<ffffffff8110a4a6>] validate_store+0xa6/0x190 > > [<ffffffff8110573c>] slab_attr_store+0x1c/0x30 > > [<ffffffff81168838>] sysfs_write_file+0xc8/0x140 > > [<ffffffff811124a3>] vfs_write+0xa3/0x160 > > [<ffffffff81112635>] sys_write+0x45/0x90 > > [<ffffffff814d3ffb>] system_call_fastpath+0x16/0x1b > > FIX anon_vma: Restoring 0xffff88020f347c80-0xffff88020f347c87=0xcc > > > Wait a minute > > You trigger this using slabinfo looping or something ? > > Bug is in slabinfo then, dont use it, and see if bug triggers. > > Given slub is now lockless, validate_slab_slab() is probably very wrong > these days. OK "slabinfo -v" is useless then. But that doesn't invalidate the BUGs that I saw during boot. They happend before I could even run slabinfo for the first time. -- Markus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>