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authorRaghavendra G <rgowdapp@redhat.com>2017-11-07 16:09:37 +0530
committerAmar Tumballi <amarts@redhat.com>2017-11-09 17:26:19 +0000
commit8b57378e5596f287a7b9d106dd6fb56a624b42ee (patch)
tree37f699e4d24e38d8ce3a6d840383ccc630317d47 /xlators/mount/fuse
parent52add0a289b8433547c5443b0dfd76e157275b10 (diff)
mount/fuse: use fstat in getattr implementation if any opened fd is available
The restriction of using fds opened by the same Pid means fds cannot be shared across threads of multithreaded application. Note that fops from kernel have different Pid for different threads. Imagine following sequence of operations: * Turn off performance.open-behind * Thread t1 opens an fd - fd1 - on file "file". Let's assume nodeid of "file" is "nodeid-file". * Thread t2 does RENAME ("newfile", "file"). Let's assume nodeid of "newfile" as "nodeid-newfile". * t2 proceeds to do fstat (fd1) The above set of operations can sometimes result in ESTALE/ENOENT errors. RENAME overwrites "file" with "newfile" changing its nodeid from "nodeid-file" to "nodeid-newfile" and post RENAME, "nodeid-file" is removed from the backend. If fstat carries nodeid-file as argument, which can happen if lookup has not refreshed the nodeid of "file" and since t2 doesn't have an fd opened, fuse_getattr_resume uses STAT which will fail as "nodeid-file" no longer exists. Since the above set of operations and sharing of fds across multiple threads are valid, this is a bug. The fix is to use any fd opened on the inode. In this specific example fuse_getattr_resume will find fd1 and winds down the call as fstat (fd1) which won't fail. Cross-checked with "Miklos Szeredi" <mszeredi.at.redhat.dot.com> for any security issues with this solution and he approves the solution. Thanks to "Miklos Szeredi" <mszeredi.at.redhat.dot.com> for all the pointers and discussions. Change-Id: I88dd29b3607cd2594eee9d72a1637b5346c8d49c BUG: 1510401 Signed-off-by: Raghavendra G <rgowdapp@redhat.com>
Diffstat (limited to 'xlators/mount/fuse')
-rw-r--r--xlators/mount/fuse/src/fuse-bridge.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/xlators/mount/fuse/src/fuse-bridge.c b/xlators/mount/fuse/src/fuse-bridge.c
index 50ac9931a5a..4e075904936 100644
--- a/xlators/mount/fuse/src/fuse-bridge.c
+++ b/xlators/mount/fuse/src/fuse-bridge.c
@@ -905,7 +905,7 @@ fuse_getattr_resume (fuse_state_t *state)
}
if (!IA_ISDIR (state->loc.inode->ia_type)) {
- state->fd = fd_lookup (state->loc.inode, state->finh->pid);
+ state->fd = fd_lookup (state->loc.inode, 0);
}
if (!state->fd) {