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A race condition existed between the time a UFS/FFS superblock check

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hash was computed and the time that the superblock was copied to a
buffer to be written to disk. The result was a failed superblock
check hash the next time that the superblock was read.

The fix is to compute the check hash after the superblock has been
copied to a buffer to be written.

PR:           236504
Reported by:  Peter Holm
Tested by:    Peter Holm
Sponsored by: Netflix
This commit is contained in:
Kirk McKusick 2019-08-06 18:10:34 +00:00
parent 7f8c266da5
commit 9454b4fd78
1 changed files with 7 additions and 1 deletions
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8
sys/ufs/ffs/ffs_vfsops.c
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@ -1998,7 +1998,13 @@ ffs_use_bwrite(void *devfd, off_t loc, void *buf, int size)
if (MOUNTEDSOFTDEP(ump->um_mountp))
softdep_setup_sbupdate(ump, (struct fs *)bp->b_data, bp);
bcopy((caddr_t)fs, bp->b_data, (u_int)fs->fs_sbsize);
ffs_oldfscompat_write((struct fs *)bp->b_data, ump);
fs = (struct fs *)bp->b_data;
ffs_oldfscompat_write(fs, ump);
/*
* Because we may have made changes to the superblock, we need to
* recompute its check-hash.
*/
fs->fs_ckhash = ffs_calc_sbhash(fs);
if (devfdp->suspended)
bp->b_flags |= B_VALIDSUSPWRT;
if (devfdp->waitfor != MNT_WAIT)