git: d91d2b513eb3 - main - geom: Handle partial I/O in g_{read,write,delete}_data()

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=d91d2b513eb30a226e87f0e52e2f9f232a2e1ca3

commit d91d2b513eb30a226e87f0e52e2f9f232a2e1ca3
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-01-20 13:25:27 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-01-20 13:29:39 +0000

    geom: Handle partial I/O in g_{read,write,delete}_data()
    
    These routines are used internally by GEOM to dispatch I/O requests to a
    provider, typically for tasting or for updating GEOM class metadata
    blocks.
    
    These routines assumed that partial I/O did not occur without setting
    BIO_ERROR, but this is possible in at least two cases:
    - Some or all of the I/O range is beyond the provider's mediasize.
      In this scenario g_io_check() truncates the bounds of the request
      before it is handed to the target provider.
    - A read from vnode-backed md(4) device returns EOF (the backing vnode
      is allowed to be smaller than the device itself) or partial vnode I/O
      occurs.
    In these scenarios g_read_data() could return a partially uninitialized
    buffer.  Many consumers are not affected by the first case, since the
    offsets used for provider metadata or tasting are relative to the
    provider's mediasize, but in some cases metadata is read at fixed
    offsets, such as when searching for a UFS superblock using the offsets
    defined by SBLOCKSEARCH.
    
    Thus, modify the routines to explicitly check for a non-zero residual
    and return EIO in that case.  Remove a related check from the
    DIOCGDELETE ioctl handler, it is handled within g_delete_data() now.
    
    Reviewed by:    mav, imp, kib
    Reported by:    KMSAN
    MFC after:      2 weeks
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D31293
---
 sys/geom/geom_dev.c | 13 -------------
 sys/geom/geom_io.c  |  6 ++++++
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/sys/geom/geom_dev.c b/sys/geom/geom_dev.c
index fedd9df96274..b94df9fcda67 100644
--- a/sys/geom/geom_dev.c
+++ b/sys/geom/geom_dev.c
@@ -654,19 +654,6 @@ g_dev_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag, struct thread
 			error = EINVAL;
 			break;
 		}
-		if ((pp->mediasize > 0) && (offset >= pp->mediasize)) {
-			/*
-			 * Catch out-of-bounds requests here. The problem is
-			 * that due to historical GEOM I/O implementation
-			 * peculatities, g_delete_data() would always return
-			 * success for requests starting just the next byte
-			 * after providers media boundary. Condition check on
-			 * non-zero media size, since that condition would
-			 * (most likely) cause ENXIO instead.
-			 */
-			error = EIO;
-			break;
-		}
 		while (length > 0) {
 			chunk = length;
 			if (g_dev_del_max_sectors != 0 &&
diff --git a/sys/geom/geom_io.c b/sys/geom/geom_io.c
index ce7f6c867388..6ec90741a7e2 100644
--- a/sys/geom/geom_io.c
+++ b/sys/geom/geom_io.c
@@ -886,6 +886,8 @@ g_read_data(struct g_consumer *cp, off_t offset, off_t length, int *error)
 	bp->bio_data = ptr;
 	g_io_request(bp, cp);
 	errorc = biowait(bp, "gread");
+	if (errorc == 0 && bp->bio_completed != length)
+		errorc = EIO;
 	if (error != NULL)
 		*error = errorc;
 	g_destroy_bio(bp);
@@ -940,6 +942,8 @@ g_write_data(struct g_consumer *cp, off_t offset, void *ptr, off_t length)
 	bp->bio_data = ptr;
 	g_io_request(bp, cp);
 	error = biowait(bp, "gwrite");
+	if (error == 0 && bp->bio_completed != length)
+		error = EIO;
 	g_destroy_bio(bp);
 	return (error);
 }
@@ -971,6 +975,8 @@ g_delete_data(struct g_consumer *cp, off_t offset, off_t length)
 	bp->bio_data = NULL;
 	g_io_request(bp, cp);
 	error = biowait(bp, "gdelete");
+	if (error == 0 && bp->bio_completed != length)
+		error = EIO;
 	g_destroy_bio(bp);
 	return (error);
 }