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authorRich Felker <dalias@aerifal.cx>2011-03-24 14:18:00 -0400
committerRich Felker <dalias@aerifal.cx>2011-03-24 14:18:00 -0400
commitb470030f839a375e5030ec9d44903ef7581c15a2 (patch)
tree462b1df89a3ea45bcf50b9d0a844472576ed6585 /src/select
parent095820016689dfdc9141f477a86de22054c86078 (diff)
downloadmusl-b470030f839a375e5030ec9d44903ef7581c15a2.tar.gz
overhaul cancellation to fix resource leaks and dangerous behavior with signals
this commit addresses two issues: 1. a race condition, whereby a cancellation request occurring after a syscall returned from kernelspace but before the subsequent CANCELPT_END would cause cancellable resource-allocating syscalls (like open) to leak resources. 2. signal handlers invoked while the thread was blocked at a cancellation point behaved as if asynchronous cancellation mode wer in effect, resulting in potentially dangerous state corruption if a cancellation request occurs. the glibc/nptl implementation of threads shares both of these issues. with this commit, both are fixed. however, cancellation points encountered in a signal handler will not be acted upon if the signal was received while the thread was already at a cancellation point. they will of course be acted upon after the signal handler returns, so in real-world usage where signal handlers quickly return, it should not be a problem. it's possible to solve this problem too by having sigaction() wrap all signal handlers with a function that uses a pthread_cleanup handler to catch cancellation, patch up the saved context, and return into the cancellable function that will catch and act upon the cancellation. however that would be a lot of complexity for minimal if any benefit...
Diffstat (limited to 'src/select')
-rw-r--r--src/select/pselect.c1
-rw-r--r--src/select/select.c1
2 files changed, 2 insertions, 0 deletions
diff --git a/src/select/pselect.c b/src/select/pselect.c
index 63ea0695..155a6eb0 100644
--- a/src/select/pselect.c
+++ b/src/select/pselect.c
@@ -10,6 +10,7 @@ int pselect(int n, fd_set *rfds, fd_set *wfds, fd_set *efds, const struct timesp
if (ts) ts_tmp = *ts;
CANCELPT_BEGIN;
r = syscall(SYS_pselect6, n, rfds, wfds, efds, ts ? &ts_tmp : 0, data);
+ CANCELPT_TRY;
CANCELPT_END;
return r;
}
diff --git a/src/select/select.c b/src/select/select.c
index 12322718..b38e7fd2 100644
--- a/src/select/select.c
+++ b/src/select/select.c
@@ -7,6 +7,7 @@ int select(int n, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeval *tv)
int r;
CANCELPT_BEGIN;
r = syscall(SYS_select, n, rfds, wfds, efds, tv);
+ CANCELPT_TRY;
CANCELPT_END;
return r;
}