Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1233487

[PATCH 4.2 105/134] fs: Dont dump core if the corefile would become world-readable.

Show all headers | View raw

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

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

From: Jann Horn <jann@thejh.net>

commit 40f705a736eac10e7dca7ab5dd5ed675a6df031d upstream.

On a filesystem like vfat, all files are created with the same owner
and mode independent of who created the file. When a vfat filesystem
is mounted with root as owner of all files and read access for everyone,
root's processes left world-readable coredumps on it (but other
users' processes only left empty corefiles when given write access
because of the uid mismatch).

Given that the old behavior was inconsistent and insecure, I don't see
a problem with changing it. Now, all processes refuse to dump core unless
the resulting corefile will only be readable by their owner.

Signed-off-by: Jann Horn <jann@thejh.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/coredump.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -685,11 +685,15 @@ void do_coredump(const siginfo_t *siginf
 		if (!S_ISREG(inode->i_mode))
 			goto close_fail;
 		/*
-		 * Dont allow local users get cute and trick others to coredump
-		 * into their pre-created files.
+		 * Don't dump core if the filesystem changed owner or mode
+		 * of the file during file creation. This is an issue when
+		 * a process dumps core while its cwd is e.g. on a vfat
+		 * filesystem.
 		 */
 		if (!uid_eq(inode->i_uid, current_fsuid()))
 			goto close_fail;
+		if ((inode->i_mode & 0677) != 0600)
+			goto close_fail;
 		if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
 			goto close_fail;
 		if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))


--
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/

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH 4.2 105/134] fs: Dont dump core if the corefile would become world-readable. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-09-27 00:00 +0200

csiph-web