Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Mon, 12 Sep 2005 19:54:33 +0200 | From | Alexander Nyberg <> | Subject | Re: 2.6.13-mm3 [OOPS] vfs, page_owner, full reproductively, badness in vsnprintf |
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On Mon, Sep 12, 2005 at 01:48:54PM +0200 Michal Piotrowski wrote:
> Hi, > > [1.] One line summary of the problem: > System oops when I do F3 (file view) in mc on /proc/page_owner > > [2.] Full description of the problem/report: > > [3.] Keywords (i.e., modules, networking, kernel): > vfs, page_owner, full reproductively > > [4.] Kernel version (from /proc/version): > Linux version 2.6.13-mm3 (root@ng02.pl) (gcc version 3.3.5 (Debian > 1:3.3.5-13)) #4 SMP PREEMPT Mon Sep 12 12:14:24 CEST 2005 >
Gah, I'm such a fantastic programmer.
I don't know what mc is up to but the error checking in read_page_owner is flawed wrt snprintf which could cause the 'size' argument to snprintf to become negative and if so overwrite beyond 'buf'.
Again, I fail to see how mc causes this to happen, but this fixes it by proper error checking.
Signed-off-by: Alexander Nyberg <alexn@telia.com>
Index: mm/fs/proc/proc_misc.c =================================================================== --- mm.orig/fs/proc/proc_misc.c 2005-09-12 16:52:22.000000000 +0200 +++ mm/fs/proc/proc_misc.c 2005-09-12 17:20:13.000000000 +0200 @@ -567,6 +567,7 @@ char namebuf[128]; unsigned long offset = 0, symsize; int i; + ssize_t num_written = 0; pfn = min_low_pfn + *ppos; page = pfn_to_page(pfn); @@ -588,22 +589,40 @@ if (!kbuf) return -ENOMEM; - ret = snprintf(kbuf, 1024, "Page allocated via order %d, mask 0x%x\n", + ret = snprintf(kbuf, count, "Page allocated via order %d, mask 0x%x\n", page->order, page->gfp_mask); + if (ret >= count) { + ret = -ENOMEM; + goto out; + } + + num_written = ret; for (i = 0; i < 8; i++) { if (!page->trace[i]) break; symname = kallsyms_lookup(page->trace[i], &symsize, &offset, &modname, namebuf); - ret += snprintf(kbuf + ret, count - ret, "[0x%lx] %s+%lu\n", + ret = snprintf(kbuf + num_written, count - num_written, "[0x%lx] %s+%lu\n", page->trace[i], namebuf, offset); + if (ret >= count - num_written) { + ret = -ENOMEM; + goto out; + } + num_written += ret; } - ret += snprintf(kbuf + ret, count -ret, "\n"); + ret = snprintf(kbuf + num_written, count - num_written, "\n"); + if (ret >= count - num_written) { + ret = -ENOMEM; + goto out; + } + + num_written += ret; + ret = num_written; if (copy_to_user(buf, kbuf, ret)) ret = -EFAULT; - +out: kfree(kbuf); return ret; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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