lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 11 Oct 2007 14:47:40 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Erez Zadok <ezk@...sunysb.edu> Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, ryan@...nie.org, cjwatson@...ntu.com, linux-mm@...ck.org Subject: Re: msync(2) bug(?), returns AOP_WRITEPAGE_ACTIVATE to userland On Sun, 7 Oct 2007 15:20:19 -0400 Erez Zadok <ezk@...sunysb.edu> wrote: > According to vfs.txt, ->writepage() may return AOP_WRITEPAGE_ACTIVATE back > to the VFS/VM. Indeed some filesystems such as tmpfs can return > AOP_WRITEPAGE_ACTIVATE; and stackable file systems (e.g., Unionfs) also > return AOP_WRITEPAGE_ACTIVATE if the lower f/s returned it. > > Anyway, some Ubuntu users of Unionfs reported that msync(2) sometimes > returns AOP_WRITEPAGE_ACTIVATE (decimal 524288) back to userland. > Therefore, some user programs fail, esp. if they're written such as this: > > err = msync(...); > if (err != 0) > // fail > > They temporarily fixed the specific program in question (apt-get) to check > > if (err < 0) > // fail > > Is this a bug indeed, or are user programs supposed to handle > AOP_WRITEPAGE_ACTIVATE (I hope not the latter). If it's a kernel bug, what > should the kernel return: a zero, or an -errno (and which one)? > shit. That's a nasty bug. Really userspace should be testing for -1, but the msync() library function should only ever return 0 or -1. Does this fix it? --- a/mm/page-writeback.c~a +++ a/mm/page-writeback.c @@ -850,8 +850,10 @@ retry: ret = (*writepage)(page, wbc, data); - if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) + if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) { unlock_page(page); + ret = 0; + } if (ret || (--(wbc->nr_to_write) <= 0)) done = 1; if (wbc->nonblocking && bdi_write_congested(bdi)) { _ - 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/
Powered by blists - more mailing lists