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util/nvmutil: further tidy up rw_file_once

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Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-13 03:44:22 +00:00
parent b4154dd29b
commit 347e39bab7
1 changed files with 11 additions and 28 deletions
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util/nvmutil/nvmutil.c
+11 -28
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@@ -1577,6 +1577,10 @@ rw_file_exact(int fd, uint8_t *mem, size_t len,
return rc; return rc;
} }
/*
* May not return all requested bytes (len).
* Use rw_file_exact for guaranteed length.
*/
static ssize_t static ssize_t
rw_file_once(int fd, uint8_t *mem, size_t len, rw_file_once(int fd, uint8_t *mem, size_t len,
off_t off, int rw_type, size_t rc) off_t off, int rw_type, size_t rc)
@@ -1584,48 +1588,27 @@ rw_file_once(int fd, uint8_t *mem, size_t len,
ssize_t rv; ssize_t rv;
size_t retries_on_zero = 0; size_t retries_on_zero = 0;
size_t max_retries = 10; size_t max_retries = 10;
read_again: read_again:
rv = do_rw(fd, mem + rc, len - rc, off + rc, rw_type); rv = do_rw(fd, mem + rc, len - rc, off + rc, rw_type);
if (rv < 0 && errno == EINTR) if (rv < 0 && errno == EINTR)
goto read_again; goto read_again;
if (rv < 0) { if (rv < 0)
errno = EIO;
return -1; return -1;
}
/* if ((size_t)rv > SSIZE_MAX /* theoretical buggy libc */
* Theoretical bug: if a buggy libc returned || (size_t)rv > (len - rc))/* don't overflow */
* a size larger than SSIZE_MAX, the cast may goto err_rw_file_once;
* cause an overflow. Specifications guarantee
* this won't happen, but spec != implementation
*/
if ((size_t)rv > SSIZE_MAX) {
errno = EIO;
return -1;
/* we do not tolerate buggy libc */
}
if (!((size_t)rv > (len - rc) /* don't overflow */ if (rv != 0)
|| rv == 0))
return rv; return rv;
/* Prevent infinite 0-byte loop */
if (rv != 0) {
errno = EIO;
return -1;
}
/*
* Fault tolerance against infinite
* zero-byte loop: re-try a finite
* number of times. This mitigates
* otherwise OK but slow filesystems
* e.g. NFS or slow media.
*/
if (retries_on_zero++ < max_retries) if (retries_on_zero++ < max_retries)
goto read_again; goto read_again;
err_rw_file_once:
errno = EIO; errno = EIO;
return -1; return -1;
} }