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Merge pull request #19116 from keszybz/readvirtualfile-opt

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Optimize read_full_virtual_file() and another coverity issue
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2021-03-29 10:51:32 +02:00
committed by GitHub
parent a81c7ac8d4 bc52deda4b
commit 8a773a30ba
3 changed files with 24 additions and 23 deletions
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43
src/basic/fileio.c
View File

@ -27,7 +27,8 @@
#include "string-util.h"
#include "tmpfile-util.h"
#define READ_FULL_BYTES_MAX (4U*1024U*1024U)
/* The maximum size of the file we'll read in one go. */
#define READ_FULL_BYTES_MAX (4U*1024U*1024U - 1)
int fopen_unlocked(const char *path, const char *options, FILE **ret) {
assert(ret);
@ -386,8 +387,10 @@ int read_full_virtual_file(const char *filename, char **ret_contents, size_t *re
/* Start size for files in /proc/ which usually report a file size of 0. (Files in /sys/ report a
* file size of 4K, which is probably OK for sizing our initial buffer, and sysfs attributes can't be
* larger anyway.) */
size = LINE_MAX / 2;
* larger anyway.)
*
* It's one less than 4k, so that the malloc() below allocates exactly 4k. */
size = 4095;
/* Limit the number of attempts to read the number of bytes returned by fstat(). */
n_retries = 3;
@ -403,22 +406,27 @@ int read_full_virtual_file(const char *filename, char **ret_contents, size_t *re
return -EBADF;
/* Be prepared for files from /proc which generally report a file size of 0. */
assert_cc(READ_FULL_BYTES_MAX < SSIZE_MAX);
if (st.st_size > 0) {
if (st.st_size > SSIZE_MAX) /* safety check in case off_t is 64bit and size_t 32bit */
if (st.st_size > READ_FULL_BYTES_MAX)
return -E2BIG;
size = st.st_size;
n_retries--;
} else
/* Double the buffer size (saturate in case of overflow) */
size = size > SSIZE_MAX / 2 ? SSIZE_MAX : size * 2;
if (size > READ_FULL_BYTES_MAX)
return -E2BIG;
} else {
/* Double the buffer size */
if (size >= READ_FULL_BYTES_MAX)
return -E2BIG;
if (size > READ_FULL_BYTES_MAX / 2 - 1)
size = READ_FULL_BYTES_MAX; /* clamp to max */
else
size = size * 2 + 1; /* Stay always one less than page size, so we malloc evenly */
}
buf = malloc(size + 1);
if (!buf)
return -ENOMEM;
size = malloc_usable_size(buf) - 1; /* Use a bigger allocation if we got it anyway */
for (;;) {
ssize_t k;
@ -462,16 +470,13 @@ int read_full_virtual_file(const char *filename, char **ret_contents, size_t *re
buf = TAKE_PTR(p);
}
if (!ret_size) {
/* Safety check: if the caller doesn't want to know the size of what we
* just read it will rely on the trailing NUL byte. But if there's an
* embedded NUL byte, then we should refuse operation as otherwise
* there'd be ambiguity about what we just read. */
if (memchr(buf, 0, n))
return -EBADMSG;
} else
if (ret_size)
*ret_size = n;
else if (memchr(buf, 0, n))
/* Safety check: if the caller doesn't want to know the size of what we just read it will
* rely on the trailing NUL byte. But if there's an embedded NUL byte, then we should refuse
* operation as otherwise there'd be ambiguity about what we just read. */
return -EBADMSG;
buf[n] = 0;
*ret_contents = TAKE_PTR(buf);

2
src/libsystemd/sd-device/test-sd-device-thread.c
View File

@ -30,8 +30,6 @@ int main(int argc, char *argv[]) {
const char *key, *value;
int r;
unsetenv("SYSTEMD_MEMPOOL");
r = sd_device_new_from_syspath(&loopback, "/sys/class/net/lo");
if (r < 0)
return handle_error_errno(r, "Failed to create loopback device object");

2
src/libudev/test-udev-device-thread.c
View File

@ -28,8 +28,6 @@ int main(int argc, char *argv[]) {
pthread_t t;
int r;
unsetenv("SYSTEMD_MEMPOOL");
loopback = udev_device_new_from_syspath(NULL, "/sys/class/net/lo");
if (!loopback)
return handle_error_errno(errno, "Failed to create loopback device object");