Commit 40f705a7 authored by Jann Horn's avatar Jann Horn Committed by Linus Torvalds
Browse files

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: default avatarJann Horn <>
Acked-by: default avatarKees Cook <>
Cc: Al Viro <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent fbb18169
...@@ -685,11 +685,15 @@ void do_coredump(const siginfo_t *siginfo) ...@@ -685,11 +685,15 @@ void do_coredump(const siginfo_t *siginfo)
if (!S_ISREG(inode->i_mode)) if (!S_ISREG(inode->i_mode))
goto close_fail; goto close_fail;
/* /*
* Dont allow local users get cute and trick others to coredump * Don't dump core if the filesystem changed owner or mode
* into their pre-created files. * 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())) if (!uid_eq(inode->i_uid, current_fsuid()))
goto close_fail; goto close_fail;
if ((inode->i_mode & 0677) != 0600)
goto close_fail;
if (!(cprm.file->f_mode & FMODE_CAN_WRITE)) if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
goto close_fail; goto close_fail;
if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file)) if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
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