From dbd9d6f8fa9c3e676e491ac65c7fa10a1af8321f Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Tue, 7 Sep 2021 20:00:29 -0700
Subject: [PATCH] fs/coredump.c: log if a core dump is aborted due to changed
file permissions
For obvious security reasons, a core dump is aborted if the filesystem
cannot preserve ownership or permissions of the dump file.
This affects filesystems like e.g. vfat, but also something like a 9pfs
share in a Qemu test setup, running as a regular user, depending on the
security model used. In those cases, the result is an empty core file and
a confused user.
To hopefully save other people a lot of time figuring out the cause, this
patch adds a simple log message for those specific cases.
[akpm@linux-foundation.org: s/|%s/%s/ in printk text]
Link: https://lkml.kernel.org/r/20210701233151.102720-1-david.oberhollenzer@sigma-star.at
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
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>
---
fs/coredump.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/coredump.c b/fs/coredump.c
index 07afb5ddb1c4e..4b3c75732c97d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -782,10 +782,17 @@ void do_coredump(const kernel_siginfo_t *siginfo)
* filesystem.
*/
mnt_userns = file_mnt_user_ns(cprm.file);
- if (!uid_eq(i_uid_into_mnt(mnt_userns, inode), current_fsuid()))
+ if (!uid_eq(i_uid_into_mnt(mnt_userns, inode),
+ current_fsuid())) {
+ pr_info_ratelimited("Core dump to %s aborted: cannot preserve file owner\n",
+ cn.corename);
goto close_fail;
- if ((inode->i_mode & 0677) != 0600)
+ }
+ if ((inode->i_mode & 0677) != 0600) {
+ pr_info_ratelimited("Core dump to %s aborted: cannot preserve file permissions\n",
+ cn.corename);
goto close_fail;
+ }
if (!(cprm.file->f_mode & FMODE_CAN_WRITE))
goto close_fail;
if (do_truncate(mnt_userns, cprm.file->f_path.dentry,
--
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