| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.2 105/134] fs: Dont dump core if the corefile would become world-readable. | Date | Sat, 26 Sep 2015 13:55:57 -0700 |
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4.2-stable review patch. If anyone has any objections, please let me know.
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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))
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