From cc85f7a634cfaf9f0713c6aa06d08817424db37a Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Mon, 1 Feb 2016 12:04:55 +0100 Subject: ALSA: rawmidi: Remove kernel WARNING for NULL user-space buffer check NULL user-space buffer can be passed even in a normal path, thus it's not good to spew a kernel warning with stack trace at each time. Just drop snd_BUG_ON() macro usage there. BugLink: http://lkml.kernel.org/r/CACT4Y+YfVJ3L+q0i-4vyQVyyPD7V=OMX0PWPi29x9Bo3QaBLdw@mail.gmail.com Reported-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/core/rawmidi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sound/core/rawmidi.c') diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c index a7759846fbaa..f75d1656272c 100644 --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -1178,7 +1178,7 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, long count1, result; struct snd_rawmidi_runtime *runtime = substream->runtime; - if (snd_BUG_ON(!kernelbuf && !userbuf)) + if (!kernelbuf && !userbuf) return -EINVAL; if (snd_BUG_ON(!runtime->buffer)) return -EINVAL; -- cgit From 06ab30034ed9c200a570ab13c017bde248ddb2a6 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Sun, 31 Jan 2016 11:57:41 +0100 Subject: ALSA: rawmidi: Make snd_rawmidi_transmit() race-free A kernel WARNING in snd_rawmidi_transmit_ack() is triggered by syzkaller fuzzer: WARNING: CPU: 1 PID: 20739 at sound/core/rawmidi.c:1136 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482 [] warn_slowpath_null+0x29/0x30 kernel/panic.c:515 [] snd_rawmidi_transmit_ack+0x275/0x400 sound/core/rawmidi.c:1136 [] snd_virmidi_output_trigger+0x4b1/0x5a0 sound/core/seq/seq_virmidi.c:163 [< inline >] snd_rawmidi_output_trigger sound/core/rawmidi.c:150 [] snd_rawmidi_kernel_write1+0x549/0x780 sound/core/rawmidi.c:1223 [] snd_rawmidi_write+0x543/0xb30 sound/core/rawmidi.c:1273 [] __vfs_write+0x113/0x480 fs/read_write.c:528 [] vfs_write+0x167/0x4a0 fs/read_write.c:577 [< inline >] SYSC_write fs/read_write.c:624 [] SyS_write+0x111/0x220 fs/read_write.c:616 [] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 Also a similar warning is found but in another path: Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [] warn_slowpath_common+0xd9/0x140 kernel/panic.c:482 [] warn_slowpath_null+0x29/0x30 kernel/panic.c:515 [] rawmidi_transmit_ack+0x24a/0x3b0 sound/core/rawmidi.c:1133 [] snd_rawmidi_transmit_ack+0x51/0x80 sound/core/rawmidi.c:1163 [] snd_virmidi_output_trigger+0x2b6/0x570 sound/core/seq/seq_virmidi.c:185 [< inline >] snd_rawmidi_output_trigger sound/core/rawmidi.c:150 [] snd_rawmidi_kernel_write1+0x4bb/0x760 sound/core/rawmidi.c:1252 [] snd_rawmidi_write+0x543/0xb30 sound/core/rawmidi.c:1302 [] __vfs_write+0x113/0x480 fs/read_write.c:528 [] vfs_write+0x167/0x4a0 fs/read_write.c:577 [< inline >] SYSC_write fs/read_write.c:624 [] SyS_write+0x111/0x220 fs/read_write.c:616 [] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185 In the former case, the reason is that virmidi has an open code calling snd_rawmidi_transmit_ack() with the value calculated outside the spinlock. We may use snd_rawmidi_transmit() in a loop just for consuming the input data, but even there, there is a race between snd_rawmidi_transmit_peek() and snd_rawmidi_tranmit_ack(). Similarly in the latter case, it calls snd_rawmidi_transmit_peek() and snd_rawmidi_tranmit_ack() separately without protection, so they are racy as well. The patch tries to address these issues by the following ways: - Introduce the unlocked versions of snd_rawmidi_transmit_peek() and snd_rawmidi_transmit_ack() to be called inside the explicit lock. - Rewrite snd_rawmidi_transmit() to be race-free (the former case). - Make the split calls (the latter case) protected in the rawmidi spin lock. BugLink: http://lkml.kernel.org/r/CACT4Y+YPq1+cYLkadwjWa5XjzF1_Vki1eHnVn-Lm0hzhSpu5PA@mail.gmail.com BugLink: http://lkml.kernel.org/r/CACT4Y+acG4iyphdOZx47Nyq_VHGbpJQK-6xNpiqUjaZYqsXOGw@mail.gmail.com Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/core/rawmidi.c | 98 ++++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 72 insertions(+), 26 deletions(-) (limited to 'sound/core/rawmidi.c') diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c index f75d1656272c..26ca02248885 100644 --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -1055,23 +1055,16 @@ int snd_rawmidi_transmit_empty(struct snd_rawmidi_substream *substream) EXPORT_SYMBOL(snd_rawmidi_transmit_empty); /** - * snd_rawmidi_transmit_peek - copy data from the internal buffer + * __snd_rawmidi_transmit_peek - copy data from the internal buffer * @substream: the rawmidi substream * @buffer: the buffer pointer * @count: data size to transfer * - * Copies data from the internal output buffer to the given buffer. - * - * Call this in the interrupt handler when the midi output is ready, - * and call snd_rawmidi_transmit_ack() after the transmission is - * finished. - * - * Return: The size of copied data, or a negative error code on failure. + * This is a variant of snd_rawmidi_transmit_peek() without spinlock. */ -int snd_rawmidi_transmit_peek(struct snd_rawmidi_substream *substream, +int __snd_rawmidi_transmit_peek(struct snd_rawmidi_substream *substream, unsigned char *buffer, int count) { - unsigned long flags; int result, count1; struct snd_rawmidi_runtime *runtime = substream->runtime; @@ -1081,7 +1074,6 @@ int snd_rawmidi_transmit_peek(struct snd_rawmidi_substream *substream, return -EINVAL; } result = 0; - spin_lock_irqsave(&runtime->lock, flags); if (runtime->avail >= runtime->buffer_size) { /* warning: lowlevel layer MUST trigger down the hardware */ goto __skip; @@ -1106,25 +1098,47 @@ int snd_rawmidi_transmit_peek(struct snd_rawmidi_substream *substream, } } __skip: + return result; +} +EXPORT_SYMBOL(__snd_rawmidi_transmit_peek); + +/** + * snd_rawmidi_transmit_peek - copy data from the internal buffer + * @substream: the rawmidi substream + * @buffer: the buffer pointer + * @count: data size to transfer + * + * Copies data from the internal output buffer to the given buffer. + * + * Call this in the interrupt handler when the midi output is ready, + * and call snd_rawmidi_transmit_ack() after the transmission is + * finished. + * + * Return: The size of copied data, or a negative error code on failure. + */ +int snd_rawmidi_transmit_peek(struct snd_rawmidi_substream *substream, + unsigned char *buffer, int count) +{ + struct snd_rawmidi_runtime *runtime = substream->runtime; + int result; + unsigned long flags; + + spin_lock_irqsave(&runtime->lock, flags); + result = __snd_rawmidi_transmit_peek(substream, buffer, count); spin_unlock_irqrestore(&runtime->lock, flags); return result; } EXPORT_SYMBOL(snd_rawmidi_transmit_peek); /** - * snd_rawmidi_transmit_ack - acknowledge the transmission + * __snd_rawmidi_transmit_ack - acknowledge the transmission * @substream: the rawmidi substream * @count: the transferred count * - * Advances the hardware pointer for the internal output buffer with - * the given size and updates the condition. - * Call after the transmission is finished. - * - * Return: The advanced size if successful, or a negative error code on failure. + * This is a variant of __snd_rawmidi_transmit_ack() without spinlock. */ -int snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int count) +int __snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int count) { - unsigned long flags; struct snd_rawmidi_runtime *runtime = substream->runtime; if (runtime->buffer == NULL) { @@ -1132,7 +1146,6 @@ int snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int count) "snd_rawmidi_transmit_ack: output is not active!!!\n"); return -EINVAL; } - spin_lock_irqsave(&runtime->lock, flags); snd_BUG_ON(runtime->avail + count > runtime->buffer_size); runtime->hw_ptr += count; runtime->hw_ptr %= runtime->buffer_size; @@ -1142,9 +1155,32 @@ int snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int count) if (runtime->drain || snd_rawmidi_ready(substream)) wake_up(&runtime->sleep); } - spin_unlock_irqrestore(&runtime->lock, flags); return count; } +EXPORT_SYMBOL(__snd_rawmidi_transmit_ack); + +/** + * snd_rawmidi_transmit_ack - acknowledge the transmission + * @substream: the rawmidi substream + * @count: the transferred count + * + * Advances the hardware pointer for the internal output buffer with + * the given size and updates the condition. + * Call after the transmission is finished. + * + * Return: The advanced size if successful, or a negative error code on failure. + */ +int snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int count) +{ + struct snd_rawmidi_runtime *runtime = substream->runtime; + int result; + unsigned long flags; + + spin_lock_irqsave(&runtime->lock, flags); + result = __snd_rawmidi_transmit_ack(substream, count); + spin_unlock_irqrestore(&runtime->lock, flags); + return result; +} EXPORT_SYMBOL(snd_rawmidi_transmit_ack); /** @@ -1160,12 +1196,22 @@ EXPORT_SYMBOL(snd_rawmidi_transmit_ack); int snd_rawmidi_transmit(struct snd_rawmidi_substream *substream, unsigned char *buffer, int count) { + struct snd_rawmidi_runtime *runtime = substream->runtime; + int result; + unsigned long flags; + + spin_lock_irqsave(&runtime->lock, flags); if (!substream->opened) - return -EBADFD; - count = snd_rawmidi_transmit_peek(substream, buffer, count); - if (count < 0) - return count; - return snd_rawmidi_transmit_ack(substream, count); + result = -EBADFD; + else { + count = __snd_rawmidi_transmit_peek(substream, buffer, count); + if (count <= 0) + result = count; + else + result = __snd_rawmidi_transmit_ack(substream, count); + } + spin_unlock_irqrestore(&runtime->lock, flags); + return result; } EXPORT_SYMBOL(snd_rawmidi_transmit); -- cgit From 81f577542af15640cbcb6ef68baa4caa610cbbfc Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 3 Feb 2016 14:41:22 +0100 Subject: ALSA: rawmidi: Fix race at copying & updating the position The rawmidi read and write functions manage runtime stream status such as runtime->appl_ptr and runtime->avail. These point where to copy the new data and how many bytes have been copied (or to be read). The problem is that rawmidi read/write call copy_from_user() or copy_to_user(), and the runtime spinlock is temporarily unlocked and relocked while copying user-space. Since the current code advances and updates the runtime status after the spin unlock/relock, the copy and the update may be asynchronous, and eventually runtime->avail might go to a negative value when many concurrent accesses are done. This may lead to memory corruption in the end. For fixing this race, in this patch, the status update code is performed in the same lock before the temporary unlock. Also, the spinlock is now taken more widely in snd_rawmidi_kernel_read1() for protecting more properly during the whole operation. BugLink: http://lkml.kernel.org/r/CACT4Y+b-dCmNf1GpgPKfDO0ih+uZCL2JV4__j-r1kdhPLSgQCQ@mail.gmail.com Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/core/rawmidi.c | 34 ++++++++++++++++++++++------------ 1 file changed, 22 insertions(+), 12 deletions(-) (limited to 'sound/core/rawmidi.c') diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c index 26ca02248885..795437b10082 100644 --- a/sound/core/rawmidi.c +++ b/sound/core/rawmidi.c @@ -942,31 +942,36 @@ static long snd_rawmidi_kernel_read1(struct snd_rawmidi_substream *substream, unsigned long flags; long result = 0, count1; struct snd_rawmidi_runtime *runtime = substream->runtime; + unsigned long appl_ptr; + spin_lock_irqsave(&runtime->lock, flags); while (count > 0 && runtime->avail) { count1 = runtime->buffer_size - runtime->appl_ptr; if (count1 > count) count1 = count; - spin_lock_irqsave(&runtime->lock, flags); if (count1 > (int)runtime->avail) count1 = runtime->avail; + + /* update runtime->appl_ptr before unlocking for userbuf */ + appl_ptr = runtime->appl_ptr; + runtime->appl_ptr += count1; + runtime->appl_ptr %= runtime->buffer_size; + runtime->avail -= count1; + if (kernelbuf) - memcpy(kernelbuf + result, runtime->buffer + runtime->appl_ptr, count1); + memcpy(kernelbuf + result, runtime->buffer + appl_ptr, count1); if (userbuf) { spin_unlock_irqrestore(&runtime->lock, flags); if (copy_to_user(userbuf + result, - runtime->buffer + runtime->appl_ptr, count1)) { + runtime->buffer + appl_ptr, count1)) { return result > 0 ? result : -EFAULT; } spin_lock_irqsave(&runtime->lock, flags); } - runtime->appl_ptr += count1; - runtime->appl_ptr %= runtime->buffer_size; - runtime->avail -= count1; - spin_unlock_irqrestore(&runtime->lock, flags); result += count1; count -= count1; } + spin_unlock_irqrestore(&runtime->lock, flags); return result; } @@ -1223,6 +1228,7 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, unsigned long flags; long count1, result; struct snd_rawmidi_runtime *runtime = substream->runtime; + unsigned long appl_ptr; if (!kernelbuf && !userbuf) return -EINVAL; @@ -1243,12 +1249,19 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, count1 = count; if (count1 > (long)runtime->avail) count1 = runtime->avail; + + /* update runtime->appl_ptr before unlocking for userbuf */ + appl_ptr = runtime->appl_ptr; + runtime->appl_ptr += count1; + runtime->appl_ptr %= runtime->buffer_size; + runtime->avail -= count1; + if (kernelbuf) - memcpy(runtime->buffer + runtime->appl_ptr, + memcpy(runtime->buffer + appl_ptr, kernelbuf + result, count1); else if (userbuf) { spin_unlock_irqrestore(&runtime->lock, flags); - if (copy_from_user(runtime->buffer + runtime->appl_ptr, + if (copy_from_user(runtime->buffer + appl_ptr, userbuf + result, count1)) { spin_lock_irqsave(&runtime->lock, flags); result = result > 0 ? result : -EFAULT; @@ -1256,9 +1269,6 @@ static long snd_rawmidi_kernel_write1(struct snd_rawmidi_substream *substream, } spin_lock_irqsave(&runtime->lock, flags); } - runtime->appl_ptr += count1; - runtime->appl_ptr %= runtime->buffer_size; - runtime->avail -= count1; result += count1; count -= count1; } -- cgit