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Fix 'kernel BUG at mm/usercopy.c'

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Fix a bug where an cgroup-OOM-killed process can cause a panic:

usercopy: Kernel memory exposure attempt detected from vmalloc (offset
1007584, size 217120)!
kernel BUG at mm/usercopy.c:102!

This was caused by zfs_uiomove() not correctly returning EFAULT
for short copies.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #15918
Closes #18408
This commit is contained in:
Tony Hutter
2026-04-23 10:52:19 -07:00
parent b8addf9221
commit aa62ae87dd
1 changed files with 10 additions and 3 deletions
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module/os/linux/zfs/zfs_uio.c
+10 -3
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@@ -234,6 +234,8 @@ zfs_uiomove_iter(void *p, size_t n, zfs_uio_rw_t rw, zfs_uio_t *uio,
boolean_t revert)
{
size_t cnt = MIN(n, uio->uio_resid);
size_t oldcnt = cnt;
int error = 0;
if (rw == UIO_READ)
cnt = copy_to_iter(p, cnt, uio->uio_iter);
@@ -249,16 +251,21 @@ zfs_uiomove_iter(void *p, size_t n, zfs_uio_rw_t rw, zfs_uio_t *uio,
return (EFAULT);
/*
* Revert advancing the uio_iter. This is set by zfs_uiocopy()
* to avoid consuming the uio and its iov_iter structure.
* When revert is set this is a zfs_uiocopy() which should not
* consume the uio and its iov_iter structure. Otherwise, it's
* a zfs_uiomove() which is expected to update the uio. Partial
* copies are allowed for both copy and move but EFAULT should
* be returned for zfs_uiomove().
*/
if (revert)
iov_iter_revert(uio->uio_iter, cnt);
else if (cnt != oldcnt)
error = EFAULT;
uio->uio_resid -= cnt;
uio->uio_loffset += cnt;
return (0);
return (error);
}
int