stable inclusion from stable-v5.10.261 commit 4817c8974315b666e895b7d1bb83cd3664c323b1 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/16595 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- POSIX requires write permission to truncate a file, so an open() that specifies O_TRUNC must be authorized for write access regardless of the O_ACCMODE access mode. nfs_open_permission_mask() builds the access mask passed to nfs_may_open(), which is the local authorization gate for OPENs the client serves itself from a cached write delegation via the can_open_delegated() path in nfs4_try_open_cached(). The mask is derived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a file the caller cannot write requests only MAY_READ and passes the local check. The OPEN is then satisfied locally and the truncation is issued to the server as a SETATTR(size=0) over the delegation stateid, which the server accepts under standard write-delegation semantics. POSIX requires that this open fail with EACCES. Include MAY_WRITE in the mask whenever O_TRUNC is set so the local check matches the access the server would have enforced. Suggested-by: Trond Myklebust <trondmy@kernel.org> Fixes: af22f94ae02a ("NFSv4: Simplify _nfs4_do_access()") Cc: stable@vger.kernel.org Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com> Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com> Signed-off-by: Lai Zewei <laizewei3@huawei.com> --- fs/nfs/dir.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 9f88ca7b2001..a6b2b2b5c5e6 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2731,6 +2731,8 @@ static int nfs_open_permission_mask(int openflags) mask |= MAY_READ; if ((openflags & O_ACCMODE) != O_RDONLY) mask |= MAY_WRITE; + if (openflags & O_TRUNC) + mask |= MAY_WRITE; } return mask; -- 2.52.0