From: Hiago De Franco Date: Mon, 13 Jan 2025 23:31:40 +0000 (-0300) Subject: eudev: backport patch to fix udevd hanging while trying to access /dev/urandom X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cd5f630581f3e38645a92ad75b496bce92b679cb;p=thirdparty%2Fopenembedded%2Fopenembedded-core-contrib.git eudev: backport patch to fix udevd hanging while trying to access /dev/urandom Linux kernel commit 48bff1053c17 ("random: opportunistically initialize on /dev/urandom reads") introduced a change where /dev/urandom blocks if the random pool is insufficiently initialized during hardware boot. This behavior causes /dev/urandom reads to hang for approximately 5 seconds, delaying the boot process with eudev init script (when it calls udevd). This issue has already been solved upstream, therefore backport the upstream patch to fix this. Signed-off-by: Hiago De Franco Signed-off-by: Mathieu Dubois-Briand --- diff --git a/meta/recipes-core/udev/eudev/0001-random-util.c-sync-dev_urandom-implementation-to-sys.patch b/meta/recipes-core/udev/eudev/0001-random-util.c-sync-dev_urandom-implementation-to-sys.patch new file mode 100644 index 00000000000..668aa731aca --- /dev/null +++ b/meta/recipes-core/udev/eudev/0001-random-util.c-sync-dev_urandom-implementation-to-sys.patch @@ -0,0 +1,138 @@ +From 95c871b7b912f39539777ac222ef7f8798bb0225 Mon Sep 17 00:00:00 2001 +From: Masahisa Kojima +Date: Thu, 25 Apr 2024 17:23:10 +0900 +Subject: [PATCH] random-util.c: sync dev_urandom implementation to + systemd-udev + +Current dev_urandom() assumes that reading /dev/urandom +will never block regardless if the random pool is fully +initialized or not. +This assumption is no longer applicable since linux kerrnel +enforces the /dev/urandom entropy initialization from +v5.18-rc2 with the commit: +48bff1053c17 ("random: opportunistically initialize on /dev/urandom reads"). + +With this, when we use the linux v5.18-rc2 or later, +dev_urandom() will block if enough random pool is not supplied. +It causes the boot delay, typically 1024msec(4msec * 256 = 1024msec) +delay to fill the 256 bits entropy for the case CONFIG_HZ=250. + +To prevent this boot delay, this commit syncs dev_urandom() +implementation to the systemd-udev. +The systemd-udev implementation of reading /dev/urandom is as follows. + - Try to get random with calling getrandom(GRND_INSECURE) + - If kernel does not support GRND_INSECURE, fallback to GRND_NONBLOCK + - If enough entropy is not supplied, fallback to reading /dev/urandom, + this will block when the kernel version is v5.18-rc2 or later + +With this modification, dev_urandom() tries not to block +as much as possible. + +This modification still keeps the backword compatibility, +dev_random() will never block if the commit(48bff1053c17) is not +applied to the linux kernel, the behavior is same as before +in this case. + +Upstream-Status: Backport [a49a3aaa460add6ae7ea208b4cac630e56fe1180] +Signed-off-by: Masahisa Kojima +--- + src/shared/missing.h | 4 +++ + src/shared/random-util.c | 70 ++++++++++++++++++---------------------- + 2 files changed, 35 insertions(+), 39 deletions(-) + +diff --git a/src/shared/missing.h b/src/shared/missing.h +index 1967840cdbf3..1caec0f9207c 100644 +--- a/src/shared/missing.h ++++ b/src/shared/missing.h +@@ -79,6 +79,10 @@ static inline int getrandom(void *buffer, size_t count, unsigned flags) { + #define GRND_RANDOM 0x0002 + #endif + ++#ifndef GRND_INSECURE ++#define GRND_INSECURE 0x0004 ++#endif ++ + #ifndef BTRFS_IOCTL_MAGIC + #define BTRFS_IOCTL_MAGIC 0x94 + #endif +diff --git a/src/shared/random-util.c b/src/shared/random-util.c +index 01a28c8ef4e9..852b00e4ce2b 100644 +--- a/src/shared/random-util.c ++++ b/src/shared/random-util.c +@@ -31,45 +31,37 @@ + #include "util.h" + + int dev_urandom(void *p, size_t n) { +- static int have_syscall = -1; +- +- _cleanup_close_ int fd = -1; +- int r; +- +- /* Gathers some randomness from the kernel. This call will +- * never block, and will always return some data from the +- * kernel, regardless if the random pool is fully initialized +- * or not. It thus makes no guarantee for the quality of the +- * returned entropy, but is good enough for or usual usecases +- * of seeding the hash functions for hashtable */ +- +- /* Use the getrandom() syscall unless we know we don't have +- * it, or when the requested size is too large for it. */ +- if (have_syscall != 0 || (size_t) (int) n != n) { +- r = getrandom(p, n, GRND_NONBLOCK); +- if (r == (int) n) { +- have_syscall = true; +- return 0; +- } +- +- if (r < 0) { +- if (errno == ENOSYS) +- /* we lack the syscall, continue with +- * reading from /dev/urandom */ +- have_syscall = false; +- else if (errno == EAGAIN) +- /* not enough entropy for now. Let's +- * remember to use the syscall the +- * next time, again, but also read +- * from /dev/urandom for now, which +- * doesn't care about the current +- * amount of entropy. */ +- have_syscall = true; +- else +- return -errno; +- } else +- /* too short read? */ +- return -ENODATA; ++ static bool have_getrandom = true, have_grndinsecure = true; ++ _cleanup_close_ int fd = -EBADF; ++ ++ if (n == 0) ++ return 0; ++ ++ for (;;) { ++ ssize_t l; ++ ++ if (!have_getrandom) ++ break; ++ ++ l = getrandom(p, n, have_grndinsecure ? GRND_INSECURE : GRND_NONBLOCK); ++ if (l > 0) { ++ if ((size_t) l == n) ++ return 0; /* Done reading, success. */ ++ p = (uint8_t *) p + l; ++ n -= l; ++ continue; /* Interrupted by a signal; keep going. */ ++ } else if (l == 0) ++ break; /* Weird, so fallback to /dev/urandom. */ ++ else if (errno == ENOSYS) { ++ have_getrandom = false; ++ break; /* No syscall, so fallback to /dev/urandom. */ ++ } else if (errno == EINVAL && have_grndinsecure) { ++ have_grndinsecure = false; ++ continue; /* No GRND_INSECURE; fallback to GRND_NONBLOCK. */ ++ } else if (errno == EAGAIN && !have_grndinsecure) ++ break; /* Will block, but no GRND_INSECURE, so fallback to /dev/urandom. */ ++ ++ break; /* Unexpected, so just give up and fallback to /dev/urandom. */ + } + + fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY); diff --git a/meta/recipes-core/udev/eudev_3.2.14.bb b/meta/recipes-core/udev/eudev_3.2.14.bb index 0e5610f77c2..b3e7d092c58 100644 --- a/meta/recipes-core/udev/eudev_3.2.14.bb +++ b/meta/recipes-core/udev/eudev_3.2.14.bb @@ -13,6 +13,7 @@ SRC_URI = "${GITHUB_BASE_URI}/download/v${PV}/${BP}.tar.gz \ file://netifnames.patch \ file://init \ file://local.rules \ + file://0001-random-util.c-sync-dev_urandom-implementation-to-sys.patch \ " SRC_URI[sha256sum] = "8da4319102f24abbf7fff5ce9c416af848df163b29590e666d334cc1927f006f"