diff options
| author | Linus Torvalds | 2020-09-29 17:18:34 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2020-09-29 17:18:34 -0700 |
| commit | 90fb702791bf99b959006972e8ee7bb4609f441b (patch) | |
| tree | 85cee49cb2af9379d7b4c58a040621122b1816ac /fs/autofs | |
| parent | ccc1d052eff9f3cfe59d201263903fe1d46c79a5 (diff) | |
autofs: use __kernel_write() for the autofs pipe writing
autofs got broken in some configurations by commit 13c164b1a186
("autofs: switch to kernel_write") because there is now an extra LSM
permission check done by security_file_permission() in rw_verify_area().
autofs is one if the few places that really does want the much more
limited __kernel_write(), because the write is an internal kernel one
that shouldn't do any user permission checks (it also doesn't need the
file_start_write/file_end_write logic, since it's just a pipe).
There are a couple of other cases like that - accounting, core dumping,
and splice - but autofs stands out because it can be built as a module.
As a result, we need to export this internal __kernel_write() function
again.
We really don't want any other module to use this, but we don't have a
"EXPORT_SYMBOL_FOR_AUTOFS_ONLY()". But we can mark it GPL-only to at
least approximate that "internal use only" for licensing.
While in this area, make autofs pass in NULL for the file position
pointer, since it's always a pipe, and we now use a NULL file pointer
for streaming file descriptors (see file_ppos() and commit 438ab720c675:
"vfs: pass ppos=NULL to .read()/.write() of FMODE_STREAM files")
This effectively reverts commits 9db977522449 ("fs: unexport
__kernel_write") and 13c164b1a186 ("autofs: switch to kernel_write").
Fixes: 13c164b1a186 ("autofs: switch to kernel_write")
Reported-by: Ondrej Mosnacek <omosnace@redhat.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/autofs')
| -rw-r--r-- | fs/autofs/waitq.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/autofs/waitq.c b/fs/autofs/waitq.c index 74c886f7c51c..5ced859dac53 100644 --- a/fs/autofs/waitq.c +++ b/fs/autofs/waitq.c @@ -53,7 +53,7 @@ static int autofs_write(struct autofs_sb_info *sbi, mutex_lock(&sbi->pipe_mutex); while (bytes) { - wr = kernel_write(file, data, bytes, &file->f_pos); + wr = __kernel_write(file, data, bytes, NULL); if (wr <= 0) break; data += wr; |