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Open Source and information security mailing list archives
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Date: Sat, 3 May 2014 22:32:48 -0400 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: Oleg Drokin <green@...uxhacker.ru> Cc: linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org, Rohit Seth <rohitseth@...gle.com> Subject: Re: [PATCH] sysctl: Fix division by zero in percpu_pagelist_fraction handler On Sat, May 03, 2014 at 09:28:03PM -0400, Oleg Drokin wrote: > percpu_pagelist_fraction_sysctl_handler calls proc_dointvec_minmax > and blindly assumes that return value of 0 means success. > In fact the other valid case is when it got a zero length input. > > After that it proceeds to a division by percpu_pagelist_fraction > value which is conveniently set to a default of zero, resulting in > division by zero. > > Other than checking the bytecount to be more than zero, perhaps > a better default value for percpu_pagelist_fraction would help too. > > [ 661.985469] divide error: 0000 [#1] SMP DEBUG_PAGEALLOC > [ 661.985868] Modules linked in: binfmt_misc cfg80211 rfkill rpcsec_gss_krb5 ttm drm_kms_helper drm i2c_piix4 microcode i2c_core joydev serio_raw pcspkr virtio_blk nfsd > [ 661.986008] CPU: 1 PID: 9142 Comm: badarea_io Not tainted 3.15.0-rc2-vm-nfs+ #19 > [ 661.986008] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 > [ 661.986008] task: ffff8800d5aeb6e0 ti: ffff8800d87a2000 task.ti: ffff8800d87a2000 > [ 661.986008] RIP: 0010:[<ffffffff81152664>] [<ffffffff81152664>] percpu_pagelist_fraction_sysctl_handler+0x84/0x120 > [ 661.988031] RSP: 0018:ffff8800d87a3e78 EFLAGS: 00010246 > [ 661.988031] RAX: 0000000000000f89 RBX: ffff88011f7fd000 RCX: 0000000000000000 > [ 661.988031] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000010 > [ 661.988031] RBP: ffff8800d87a3e98 R08: ffffffff81d002c8 R09: ffff8800d87a3f50 > [ 661.988031] R10: 000000000000000b R11: 0000000000000246 R12: 0000000000000060 > [ 661.988031] R13: ffffffff81c3c3e0 R14: ffffffff81cfddf8 R15: ffff8801193b0800 > [ 661.988031] FS: 00007f614f1e9740(0000) GS:ffff88011f440000(0000) knlGS:0000000000000000 > [ 661.988031] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [ 661.988031] CR2: 00007f614f1fa000 CR3: 00000000d9291000 CR4: 00000000000006e0 > [ 661.988031] Stack: > [ 661.988031] 0000000000000001 ffffffffffffffea ffffffff81c3c3e0 0000000000000000 > [ 661.988031] ffff8800d87a3ee8 ffffffff8122b163 ffff8800d87a3f50 00007fff1564969c > [ 661.988031] 0000000000000000 ffff8800d8098f00 00007fff1564969c ffff8800d87a3f50 > [ 661.988031] Call Trace: > [ 661.988031] [<ffffffff8122b163>] proc_sys_call_handler+0xb3/0xc0 > [ 661.988031] [<ffffffff8122b184>] proc_sys_write+0x14/0x20 > [ 661.988031] [<ffffffff811ba93a>] vfs_write+0xba/0x1e0 > [ 661.988031] [<ffffffff811bb486>] SyS_write+0x46/0xb0 > [ 661.988031] [<ffffffff816db7ff>] tracesys+0xe1/0xe6 > [ 661.988031] Code: 1f 84 00 00 00 00 00 48 83 bb b0 06 00 00 00 0f 84 7c 00 00 00 48 63 0d 93 6a e1 00 48 8b 83 b8 06 00 00 31 d2 41 bc 60 00 00 00 <48> f7 f1 ba 01 00 00 00 49 89 c5 48 c1 e8 02 48 85 c0 48 0f 44 > > Signed-off-by: Oleg Drokin <green@...uxhacker.ru> > CC: Rohit Seth <rohitseth@...gle.com> Why are you sending this to me? Please use scripts/get_maintainer.pl to find the people, and mailing lists, that this patch should be sent to. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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