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authorRussell King <rmk+kernel@arm.linux.org.uk>2012-02-08 17:13:41 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-02-08 19:03:51 -0800
commit025e4ab3db07fcbf62c01e4f30d1012234beb980 (patch)
treec23464148c67894ad23cd8c3b0c45fb8ad4e3660
parentb9980cdcf2524c5fe15d8cbae9c97b3ed6385563 (diff)
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pcmcia: fix socket refcount decrementing on each resume
This fixes a memory-corrupting bug: not only does it cause the warning, but as a result of dropping the refcount to zero, it causes the pcmcia_socket0 device structure to be freed while it still has references, causing slab caches corruption. A fatal oops quickly follows this warning - often even just a 'dmesg' following the warning causes the kernel to oops. While testing suspend/resume on an ARM device with PCMCIA support, and a CF card inserted, I found that after five suspend and resumes, the kernel would complain, and shortly die after with slab corruption. WARNING: at include/linux/kref.h:41 kobject_get+0x28/0x50() As the message doesn't give a clue about which kobject, and the built-in debugging in drivers/base/power/main.c happens too late, this was added right before each get_device(): printk("%s: %p [%s] %u\n", __func__, dev, kobject_name(&dev->kobj), atomic_read(&dev->kobj.kref.refcount)); and on the 3rd s2ram cycle, the following behaviour observed: On the 3rd suspend/resume cycle: dpm_prepare: c1a0d998 [pcmcia_socket0] 3 dpm_suspend: c1a0d998 [pcmcia_socket0] 3 dpm_suspend_noirq: c1a0d998 [pcmcia_socket0] 3 dpm_resume_noirq: c1a0d998 [pcmcia_socket0] 3 dpm_resume: c1a0d998 [pcmcia_socket0] 3 dpm_complete: c1a0d998 [pcmcia_socket0] 2 4th: dpm_prepare: c1a0d998 [pcmcia_socket0] 2 dpm_suspend: c1a0d998 [pcmcia_socket0] 2 dpm_suspend_noirq: c1a0d998 [pcmcia_socket0] 2 dpm_resume_noirq: c1a0d998 [pcmcia_socket0] 2 dpm_resume: c1a0d998 [pcmcia_socket0] 2 dpm_complete: c1a0d998 [pcmcia_socket0] 1 5th: dpm_prepare: c1a0d998 [pcmcia_socket0] 1 dpm_suspend: c1a0d998 [pcmcia_socket0] 1 dpm_suspend_noirq: c1a0d998 [pcmcia_socket0] 1 dpm_resume_noirq: c1a0d998 [pcmcia_socket0] 1 dpm_resume: c1a0d998 [pcmcia_socket0] 1 dpm_complete: c1a0d998 [pcmcia_socket0] 0 ------------[ cut here ]------------ WARNING: at include/linux/kref.h:41 kobject_get+0x28/0x50() Modules linked in: ucb1x00_core Backtrace: [<c0212090>] (dump_backtrace+0x0/0x110) from [<c04799dc>] (dump_stack+0x18/0x1c) [<c04799c4>] (dump_stack+0x0/0x1c) from [<c021cba0>] (warn_slowpath_common+0x50/0x68) [<c021cb50>] (warn_slowpath_common+0x0/0x68) from [<c021cbdc>] (warn_slowpath_null+0x24/0x28) [<c021cbb8>] (warn_slowpath_null+0x0/0x28) from [<c0335374>] (kobject_get+0x28/0x50) [<c033534c>] (kobject_get+0x0/0x50) from [<c03804f4>] (get_device+0x1c/0x24) [<c0388c90>] (dpm_complete+0x0/0x1a0) from [<c0389cc0>] (dpm_resume_end+0x1c/0x20) ... Looking at commit 7b24e7988263 ("pcmcia: split up central event handler"), the following change was made to cs.c: return 0; } #endif - - send_event(skt, CS_EVENT_PM_RESUME, CS_EVENT_PRI_LOW); + if (!(skt->state & SOCKET_CARDBUS) && (skt->callback)) + skt->callback->early_resume(skt); return 0; } And the corresponding change in ds.c is from: -static int ds_event(struct pcmcia_socket *skt, event_t event, int priority) -{ - struct pcmcia_socket *s = pcmcia_get_socket(skt); ... - switch (event) { ... - case CS_EVENT_PM_RESUME: - if (verify_cis_cache(skt) != 0) { - dev_dbg(&skt->dev, "cis mismatch - different card\n"); - /* first, remove the card */ - ds_event(skt, CS_EVENT_CARD_REMOVAL, CS_EVENT_PRI_HIGH); - mutex_lock(&s->ops_mutex); - destroy_cis_cache(skt); - kfree(skt->fake_cis); - skt->fake_cis = NULL; - s->functions = 0; - mutex_unlock(&s->ops_mutex); - /* now, add the new card */ - ds_event(skt, CS_EVENT_CARD_INSERTION, - CS_EVENT_PRI_LOW); - } - break; ... - } - pcmcia_put_socket(s); - return 0; -} /* ds_event */ to: +static int pcmcia_bus_early_resume(struct pcmcia_socket *skt) +{ + if (!verify_cis_cache(skt)) { + pcmcia_put_socket(skt); + return 0; + } + dev_dbg(&skt->dev, "cis mismatch - different card\n"); + /* first, remove the card */ + pcmcia_bus_remove(skt); + mutex_lock(&skt->ops_mutex); + destroy_cis_cache(skt); + kfree(skt->fake_cis); + skt->fake_cis = NULL; + skt->functions = 0; + mutex_unlock(&skt->ops_mutex); + /* now, add the new card */ + pcmcia_bus_add(skt); + return 0; +} As can be seen, the original function called pcmcia_get_socket() and pcmcia_put_socket() around the guts, whereas the replacement code calls pcmcia_put_socket() only in one path. This creates an imbalance in the refcounting. Testing with pcmcia_put_socket() put removed shows that the bug is gone: dpm_suspend: c1a10998 [pcmcia_socket0] 5 dpm_suspend_noirq: c1a10998 [pcmcia_socket0] 5 dpm_resume_noirq: c1a10998 [pcmcia_socket0] 5 dpm_resume: c1a10998 [pcmcia_socket0] 5 dpm_complete: c1a10998 [pcmcia_socket0] 5 Tested-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/pcmcia/ds.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/drivers/pcmcia/ds.c b/drivers/pcmcia/ds.c
index 749c2a16012..1932029de48 100644
--- a/drivers/pcmcia/ds.c
+++ b/drivers/pcmcia/ds.c
@@ -1269,10 +1269,8 @@ static int pcmcia_bus_add(struct pcmcia_socket *skt)
static int pcmcia_bus_early_resume(struct pcmcia_socket *skt)
{
- if (!verify_cis_cache(skt)) {
- pcmcia_put_socket(skt);
+ if (!verify_cis_cache(skt))
return 0;
- }
dev_dbg(&skt->dev, "cis mismatch - different card\n");