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| author |  Thomas Petazzoni <thomas.petazzoni@bootlin.com> | 2018-09-19 08:44:24 +0200 |
|---|---|---|
| committer |  Peter Korsgaard <peter@korsgaard.com> | 2018-09-20 07:06:58 +0200 |
| commit | 1f90976c88f1e4a910f2fb55a331e3fc1048d62d (patch) | |
| tree | 5c7aef14c87d74a4eef19d124de6bc5a09748792 | |
| parent | adc98bfa260569c844843934768b0ae77cf64a86 (diff) | |
| download | buildroot-1f90976c88f1e4a910f2fb55a331e3fc1048d62d.tar.gz buildroot-1f90976c88f1e4a910f2fb55a331e3fc1048d62d.tar.bz2 | |
musl: add upstream patch to fix race condition in file locking
According to [1]:
musl 1.1.20 introduced a regression in stdio FILE locking that can
cause soft deadlocks with >2 threads contending for a
FILE. Users/dists should apply
https://git.musl-libc.org/cgit/musl/commit/?id=0db393d3a77bb9f300a356c6a5484fc2dddb161d.
[1] https://twitter.com/musllibc/status/1042292786568024070
This commit therefore adds the corresponding patch to the musl
package.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
| -rw-r--r-- | package/musl/0002-fix-race-condition-in-file-locking.patch | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/package/musl/0002-fix-race-condition-in-file-locking.patch b/package/musl/0002-fix-race-condition-in-file-locking.patch new file mode 100644 index 0000000000..f3e85e6888 --- /dev/null +++ b/package/musl/0002-fix-race-condition-in-file-locking.patch @@ -0,0 +1,55 @@ +From 0db393d3a77bb9f300a356c6a5484fc2dddb161d Mon Sep 17 00:00:00 2001 +From: Kaarle Ritvanen <kaarle.ritvanen@datakunkku.fi> +Date: Tue, 18 Sep 2018 10:03:27 +0300 +Subject: [PATCH] fix race condition in file locking + +The condition occurs when +- thread #1 is holding the lock +- thread #2 is waiting for it on __futexwait +- thread #1 is about to release the lock and performs a_swap +- thread #3 enters the __lockfile function and manages to grab the lock + before thread #1 calls __wake, resetting the MAYBE_WAITERS flag +- thread #1 calls __wake +- thread #2 wakes up but goes again to __futexwait as the lock is + held by thread #3 +- thread #3 releases the lock but does not call __wake as the + MAYBE_WAITERS flag is not set + +This condition results in thread #2 not being woken up. This patch fixes +the problem by making the woken up thread ensure that the flag is +properly set before going to sleep again. + +Mainainer's note: This fixes a regression introduced in commit +c21f750727515602a9e84f2a190ee8a0a2aeb2a1. +Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com> +--- + src/stdio/__lockfile.c | 12 ++++++------ + 1 file changed, 6 insertions(+), 6 deletions(-) + +diff --git a/src/stdio/__lockfile.c b/src/stdio/__lockfile.c +index 2ff75d8a..0dcb2a42 100644 +--- a/src/stdio/__lockfile.c ++++ b/src/stdio/__lockfile.c +@@ -8,13 +8,13 @@ int __lockfile(FILE *f) + int owner = f->lock, tid = __pthread_self()->tid; + if ((owner & ~MAYBE_WAITERS) == tid) + return 0; +- for (;;) { +- owner = a_cas(&f->lock, 0, tid); +- if (!owner) return 1; +- if (a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner) break; ++ owner = a_cas(&f->lock, 0, tid); ++ if (!owner) return 1; ++ while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) { ++ if ((owner & MAYBE_WAITERS) || ++ a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner) ++ __futexwait(&f->lock, owner|MAYBE_WAITERS, 1); + } +- while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) +- __futexwait(&f->lock, owner, 1); + return 1; + } + +-- +2.14.4 + |