Messages in this thread | | | Date | Thu, 18 Nov 2010 23:41:24 +0200 | From | Pekka Enberg <> | Subject | Re: [PATCH] slub: operate cache name memory same to slab and slob |
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On 18.11.2010 23.15, Matt Mackall wrote: > On Thu, 2010-11-18 at 11:00 +0800, b32542@freescale.com wrote: >> From: Zeng Zhaoming<zengzm.kernel@gmail.com> >> >> Get a memory leak complaint about ext4: >> comm "mount", pid 1159, jiffies 4294904647 (age 6077.804s) >> hex dump (first 32 bytes): >> 65 78 74 34 5f 67 72 6f 75 70 69 6e 66 6f 5f 31 ext4_groupinfo_1 >> 30 00 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 0.kkkkkkkkkkkkk. >> backtrace: >> [<c068ade3>] kmemleak_alloc+0x93/0xd0 >> [<c024e54c>] __kmalloc_track_caller+0x30c/0x380 >> [<c02269d3>] kstrdup+0x33/0x60 >> [<c0318a70>] ext4_mb_init+0x4e0/0x550 >> [<c0304e0e>] ext4_fill_super+0x1e6e/0x2f60 >> [<c0261140>] mount_bdev+0x1c0/0x1f0 >> [<c02fc00f>] ext4_mount+0x1f/0x30 >> [<c02603d8>] vfs_kern_mount+0x78/0x250 >> [<c026060e>] do_kern_mount+0x3e/0x100 >> [<c027b4c2>] do_mount+0x2e2/0x780 >> [<c027ba04>] sys_mount+0xa4/0xd0 >> [<c010429f>] sysenter_do_call+0x12/0x38 >> [<ffffffff>] 0xffffffff >> >> It is cause by slub manage the cache name different from slab and slob. >> In slab and slob, only reference to name, alloc and reclaim the memory >> is the duty of the code that invoked kmem_cache_create(). >> >> In slub, cache name duplicated when create. This ambiguity will cause >> some memory leaks and double free if kmem_cache_create() pass a >> dynamic malloc cache name. > > I don't get it. > > Caller allocates X, passes X to slub, slub duplicates X as X', and > properly frees X', then caller frees X. Yes, that's silly, but where's > the leak? > > But slub and slab should obviously both manage names in the same way, > namely the historical "caller allocates" way. So: > > Acked-by: Matt Mackall<mpm@selenic.com>
The kstrdup() is there because of SLUB cache merging. See commit 84c1cf62465e2fb0a692620dcfeb52323ab03d48 ("SLUB: Fix merged slab cache names") for details.
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