The patch titled
Subject: fs: Don't dump core if the corefile would become world-readable.
has been added to the -mm tree. Its filename is
fs-dont-dump-core-if-the-corefile-would-become-world-readable.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-dont-dump-core-if-the-corefile-would-become-world-readable.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-dont-dump-core-if-the-corefile-would-become-world-readable.patch
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------------------------------------------------------
From: Jann Horn <jann@xxxxxxxxx>
Subject: fs: Don't dump core if the corefile would become world-readable.
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@xxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/coredump.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff -puN fs/coredump.c~fs-dont-dump-core-if-the-corefile-would-become-world-readable fs/coredump.c
--- a/fs/coredump.c~fs-dont-dump-core-if-the-corefile-would-become-world-readable
+++ a/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))
_
Patches currently in -mm which might be from jann@xxxxxxxxx are
fs-if-a-coredump-already-exists-unlink-and-recreate-with-o_excl.patch
fs-dont-dump-core-if-the-corefile-would-become-world-readable.patch
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