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nvmutil: stronger race-condition check on prw

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do it per read, in the fallback pread/pwrite

per read/write that is

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-15 01:43:35 +00:00
parent a050e5a563
commit 7f192b4344
1 changed files with 23 additions and 18 deletions
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util/nvmutil/nvmutil.c
+23 -18
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@@ -2097,25 +2097,30 @@ real_pread_pwrite:
return -1; return -1;
} }
verified = lseek_loop(fd, (off_t)0, SEEK_CUR,
loop_eagain, loop_eintr);
/*
* Verify again before I/O
* (even with OFF_ERR)
*
* This implements the first check
* even with OFF_ERR, but without
* the recovery. On ERR_RESET, if
* the check fails again, then we
* know something else is touching
* the file, so it's best that we
* probably leave it alone and err.
*/
if (verified != off)
goto err_prw;
do { do {
/*
* Verify again before I/O
* (even with OFF_ERR)
*
* This implements the first check
* even with OFF_ERR, but without
* the recovery. On ERR_RESET, if
* the check fails again, then we
* know something else is touching
* the file, so it's best that we
* probably leave it alone and err.
*
* In other words, ERR_RESET only
* tolerates one change. Any more
* will cause an exit, including
* per EINTR/EAGAIN re-spin.
*/
verified = lseek_loop(fd, (off_t)0, SEEK_CUR,
loop_eagain, loop_eintr);
if (verified != off)
goto err_prw;
if (rw_type == IO_PREAD) if (rw_type == IO_PREAD)
r = read(fd, mem, nrw); r = read(fd, mem, nrw);
else if (rw_type == IO_PWRITE) else if (rw_type == IO_PWRITE)