linux-kernel - [PATCH 3.4 23/35] fs/proc/base.c: fix GPF in /proc/$PID/map

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Message-Id: <20140321001054.926431163@linuxfoundation.org>
Date:	Thu, 20 Mar 2014 17:11:14 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Artem Fetishev <artem_fetishev@...m.com>,
	Aleksandr Terekhov <aleksandr_terekhov@...m.com>,
	wiebittewas@...il.com, Pavel Emelyanov <xemul@...allels.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.4 23/35] fs/proc/base.c: fix GPF in /proc/$PID/map_files

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Artem Fetishev <artem_fetishev@...m.com>

commit 70335abb2689c8cd5df91bf2d95a65649addf50b upstream.

The expected logic of proc_map_files_get_link() is either to return 0
and initialize 'path' or return an error and leave 'path' uninitialized.

By the time dname_to_vma_addr() returns 0 the corresponding vma may have
already be gone.  In this case the path is not initialized but the
return value is still 0.  This results in 'general protection fault'
inside d_path().

Steps to reproduce:

  CONFIG_CHECKPOINT_RESTORE=y

    fd = open(...);
    while (1) {
        mmap(fd, ...);
        munmap(fd, ...);
    }

  ls -la /proc/$PID/map_files

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=68991

Signed-off-by: Artem Fetishev <artem_fetishev@...m.com>
Signed-off-by: Aleksandr Terekhov <aleksandr_terekhov@...m.com>
Reported-by: <wiebittewas@...il.com>
Acked-by: Pavel Emelyanov <xemul@...allels.com>
Acked-by: Cyrill Gorcunov <gorcunov@...nvz.org>
Reviewed-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/proc/base.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2092,6 +2092,7 @@ static int proc_map_files_get_link(struc
 	if (rc)
 		goto out_mmput;

+	rc = -ENOENT;
 	down_read(&mm->mmap_sem);
 	vma = find_exact_vma(mm, vm_start, vm_end);
 	if (vma && vma->vm_file) {

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