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auxdisplay: charlcd: properly restore atomic counter on error path
Commitf4757af
("staging: panel: Fix single-open policy race condition") introduced in 3.19-rc1 attempted to fix a race condition on the open, but failed to properly do it and used to exit without restoring the semaphore. This results in -EBUSY being returned after the first open error until the module is reloaded or the system restarted (ie: consecutive to a dual open resulting in -EBUSY or to a permission error). [ Note for stable maintainers: the code moved from drivers/misc/panel.c to drivers/auxdisplay/{charlcd,panel}.c during 4.12. The patch easily applies there (modulo the renamed atomic counter) but I can provide a tested backport if desired. ] Fixes:f4757af85
# 3.19-rc1 Cc: stable@vger.kernel.org Cc: Mariusz Gorski <marius.gorski@gmail.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com> Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -647,18 +647,25 @@ static ssize_t charlcd_write(struct file *file, const char __user *buf,
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static int charlcd_open(struct inode *inode, struct file *file)
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{
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struct charlcd_priv *priv = to_priv(the_charlcd);
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int ret;
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ret = -EBUSY;
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if (!atomic_dec_and_test(&charlcd_available))
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return -EBUSY; /* open only once at a time */
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goto fail; /* open only once at a time */
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ret = -EPERM;
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if (file->f_mode & FMODE_READ) /* device is write-only */
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return -EPERM;
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goto fail;
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if (priv->must_clear) {
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charlcd_clear_display(&priv->lcd);
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priv->must_clear = false;
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}
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return nonseekable_open(inode, file);
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fail:
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atomic_inc(&charlcd_available);
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return ret;
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}
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static int charlcd_release(struct inode *inode, struct file *file)
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@ -1105,14 +1105,21 @@ static ssize_t keypad_read(struct file *file,
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static int keypad_open(struct inode *inode, struct file *file)
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{
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if (!atomic_dec_and_test(&keypad_available))
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return -EBUSY; /* open only once at a time */
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int ret;
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ret = -EBUSY;
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if (!atomic_dec_and_test(&keypad_available))
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goto fail; /* open only once at a time */
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ret = -EPERM;
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if (file->f_mode & FMODE_WRITE) /* device is read-only */
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return -EPERM;
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goto fail;
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keypad_buflen = 0; /* flush the buffer on opening */
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return 0;
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fail:
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atomic_inc(&keypad_available);
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return ret;
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}
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static int keypad_release(struct inode *inode, struct file *file)
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