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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>
This commit is contained in:
David Oberhollenzer 2021-09-07 20:00:29 -07:00 committed by Linus Torvalds
parent 98e2e409e7
commit dbd9d6f8fa
1 changed files with 9 additions and 2 deletions
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11
fs/coredump.c
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@ -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,