From dbd9d6f8fa9c3e676e491ac65c7fa10a1af8321f Mon Sep 17 00:00:00 2001 From: David Oberhollenzer 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 Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/coredump.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 07afb5ddb1c4..4b3c75732c97 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,