Re: [PATCH v5 14/23] fanotify: Encode invalid file handler when no inode is provided
From: Jan Kara <jack@suse.cz>
Date: 2021-08-05 09:56:21
Also in:
linux-api, linux-fsdevel
On Wed 04-08-21 12:06:03, Gabriel Krisman Bertazi wrote:
Instead of failing, encode an invalid file handler in fanotify_encode_fh if no inode is provided. This bogus file handler will be reported by FAN_FS_ERROR for non-inode errors. Also adjust the single caller that might rely on failure after passing an empty inode.
It is not 'file handler' but rather 'file handle' - several times in the changelog and in subject :).
quoted hunk ↗ jump to hunk
Suggested-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Gabriel Krisman Bertazi <redacted> --- fs/notify/fanotify/fanotify.c | 39 ++++++++++++++++++++--------------- fs/notify/fanotify/fanotify.h | 6 ++++-- 2 files changed, 26 insertions(+), 19 deletions(-)diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index 0d6ba218bc01..456c60107d88 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c@@ -349,12 +349,6 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, void *buf = fh->buf; int err; - fh->type = FILEID_ROOT; - fh->len = 0; - fh->flags = 0; - if (!inode) - return 0; -
I'd keep the fh->flags initialization here. Otherwise it will not be initialized on some error returns.
quoted hunk ↗ jump to hunk
@@ -363,8 +357,9 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, if (fh_len < 4 || WARN_ON_ONCE(fh_len % 4)) goto out_err; - /* No external buffer in a variable size allocated fh */ - if (gfp && fh_len > FANOTIFY_INLINE_FH_LEN) { + fh->flags = 0; + /* No external buffer in a variable size allocated fh or null fh */ + if (inode && gfp && fh_len > FANOTIFY_INLINE_FH_LEN) { /* Treat failure to allocate fh as failure to encode fh */ err = -ENOMEM; ext_buf = kmalloc(fh_len, gfp);@@ -376,14 +371,24 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, fh->flags |= FANOTIFY_FH_FLAG_EXT_BUF; } - dwords = fh_len >> 2; - type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL); - err = -EINVAL; - if (!type || type == FILEID_INVALID || fh_len != dwords << 2) - goto out_err; - - fh->type = type; - fh->len = fh_len; + if (inode) { + dwords = fh_len >> 2; + type = exportfs_encode_inode_fh(inode, buf, &dwords, NULL); + err = -EINVAL; + if (!type || type == FILEID_INVALID || fh_len != dwords << 2) + goto out_err; + fh->type = type; + fh->len = fh_len; + } else { + /* + * Invalid FHs are used on FAN_FS_ERROR for errors not + * linked to any inode. Caller needs to guarantee the fh + * has at least FANOTIFY_NULL_FH_LEN bytes of space. + */ + fh->type = FILEID_INVALID; + fh->len = FANOTIFY_NULL_FH_LEN; + memset(buf, 0, FANOTIFY_NULL_FH_LEN); + }
Maybe it will become clearer later during the series but why do you set fh->len to FANOTIFY_NULL_FH_LEN and not 0? Honza -- Jan Kara [off-list ref] SUSE Labs, CR