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authorAnton Ivanov <anton.ivanov@cambridgegreys.com>2020-12-07 17:19:39 +0000
committerRichard Weinberger <richard@nod.at>2020-12-13 22:38:28 +0100
commit9b1c0c0e25dcccafd30e7d4c150c249cc65550eb (patch)
tree0e5ea2689996194fbe6588145dc72fc4033b3355
parente3a01cbee9c5f2c6fc813dd6af007716e60257e7 (diff)
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um: tty: Fix handling of close in tty lines
Fix a logical error in tty reading. We get 0 and errno == EAGAIN on the first attempt to read from a closed file descriptor. Compared to that a true EAGAIN is EAGAIN and -1. If we check errno for EAGAIN first, before checking the return value we miss the fact that the descriptor is closed. This bug is as old as the driver. It was not showing up with the original POLL based IRQ controller, because it was producing multiple events. Switching to EPOLL unmasked it. Fixes: ff6a17989c08 ("Epoll based IRQ controller") Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com> Signed-off-by: Richard Weinberger <richard@nod.at>
-rw-r--r--arch/um/drivers/chan_user.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index 4d80526a4236..d8845d4aac6a 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -26,10 +26,10 @@ int generic_read(int fd, char *c_out, void *unused)
n = read(fd, c_out, sizeof(*c_out));
if (n > 0)
return n;
- else if (errno == EAGAIN)
- return 0;
else if (n == 0)
return -EIO;
+ else if (errno == EAGAIN)
+ return 0;
return -errno;
}