linux-kernel - [PATCH] procfs: fix mmap() for /proc/vmcore

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Date:   Sat, 19 May 2018 05:15:23 +0200
From:   Vasily Gorbik <gor@...ux.ibm.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>
Cc:     linux-kernel@...r.kernel.org,
        Heiko Carstens <heiko.carstens@...ibm.com>
Subject: [PATCH] procfs: fix mmap() for /proc/vmcore

Procfs does not set max file size (s_maxbytes) and ends up with default
value of
MAX_NON_LFS	 ((1UL<<31) - 1)
Commit be83bbf80682 ("mmap: introduce sane default mmap limits")
introduced "pgoff" limits checks for mmap, considering fs max file size
as upper limit, which made it impossible to mmap /proc/vmcore file
contents above 2Gb (/proc/vmcore appears to be the only procfs file
supporting mmap).

Reuse MAX_LFS_FILESIZE as procfs s_maxbytes value.

Fixes: be83bbf80682 ("mmap: introduce sane default mmap limits")
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
---
 fs/proc/inode.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 2cf3b74391ca..de1b3b1da883 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -502,6 +502,7 @@ int proc_fill_super(struct super_block *s, void *data, int silent)
 	/* User space would break if executables or devices appear on proc */
 	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
 	s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
+	s->s_maxbytes = MAX_LFS_FILESIZE;
 	s->s_blocksize = 1024;
 	s->s_blocksize_bits = 10;
 	s->s_magic = PROC_SUPER_MAGIC;
-- 
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