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author | Rich Felker <dalias@aerifal.cx> | 2011-03-24 14:18:00 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2011-03-24 14:18:00 -0400 |
commit | b470030f839a375e5030ec9d44903ef7581c15a2 (patch) | |
tree | 462b1df89a3ea45bcf50b9d0a844472576ed6585 /src/process | |
parent | 095820016689dfdc9141f477a86de22054c86078 (diff) | |
download | musl-b470030f839a375e5030ec9d44903ef7581c15a2.zip musl-b470030f839a375e5030ec9d44903ef7581c15a2.tar.gz musl-b470030f839a375e5030ec9d44903ef7581c15a2.tar.bz2 |
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/process')
-rw-r--r-- | src/process/waitid.c | 8 | ||||
-rw-r--r-- | src/process/waitpid.c | 8 |
2 files changed, 14 insertions, 2 deletions
diff --git a/src/process/waitid.c b/src/process/waitid.c index b1e5e9b..4fa7c02 100644 --- a/src/process/waitid.c +++ b/src/process/waitid.c @@ -1,7 +1,13 @@ #include <sys/wait.h> #include "syscall.h" +#include "libc.h" int waitid(idtype_t type, id_t id, siginfo_t *info, int options) { - return syscall(SYS_waitid, type, id, info, options, 0); + int r; + CANCELPT_BEGIN; + r = syscall(SYS_waitid, type, id, info, options, 0); + if (r<0) CANCELPT_TRY; + CANCELPT_END; + return r; } diff --git a/src/process/waitpid.c b/src/process/waitpid.c index ec2757b..5e0320f 100644 --- a/src/process/waitpid.c +++ b/src/process/waitpid.c @@ -1,7 +1,13 @@ #include <sys/wait.h> #include "syscall.h" +#include "libc.h" pid_t waitpid(pid_t pid, int *status, int options) { - return syscall(SYS_wait4, pid, status, options, 0); + int r; + CANCELPT_BEGIN; + r = syscall(SYS_wait4, pid, status, options, 0); + if (r<0) CANCELPT_TRY; + CANCELPT_END; + return r; } |