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Linux Security Module listsecurity (and security xattr hooks) only one called?
by Pasquier, Thomas Sept. 5, 2016

Sept. 5, 2016

In security/security.c (see here: https://github.com/torvalds/linux/blob/835c92d43b29eb354abdbd5475308a474d7e… ) Looking at this: int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size) { if (unlikely(IS_PRIVATE(inode))) return 0; return call_int_hook(inode_listsecurity, 0, inode, buffer, buffer_size); } One would expect all stacked security module to be called. However, when looking at this: #define call_int_hook(FUNC, IRC, ...) ({ \ int RC = IRC; \ do { \ struct security_hook_list *P; \ \ list_for_each_entry(P, &security_hook_heads.FUNC, list) { \ RC = P->hook.FUNC(__VA_ARGS__); \ if (RC != 0) \ break; \ } \ } while (0); \ RC; \ }) If one of the module return a non-zero value, the other are not called. That means that the list of security of xattr is not built (or rather that it only contains the first module being called), as the lenght of inserted element is returned. Similarly for setsecurity and getsecurity, it seems that only one module will be called as if the given module does not support the security xattr, it returns -EOPNOTSUPP (instead I believe the next module being called, until one supporting the attribute is met). What is the rational here? I could change the code to support multiple security xattr, but don't want to do so before I understand why it was done like this. Any help is welcome.

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How is vmap_area inserted and can map_areas overlap?
by Peng Gao Sept. 4, 2016

Sept. 4, 2016

I am browsing the code static void __insert_vmap_area(struct vmap_area *va) { struct rb_node **p = &vmap_area_root.rb_node; struct rb_node *parent = NULL; struct rb_node *tmp; while (*p) { struct vmap_area *tmp_va; parent = *p; tmp_va = rb_entry(parent, struct vmap_area, rb_node); if (va->va_start < tmp_va->va_end) p = &(*p)->rb_left; else if (va->va_end > tmp_va->va_start) p = &(*p)->rb_right; else BUG(); } rb_link_node(&va->rb_node, parent, p); rb_insert_color(&va->rb_node, &vmap_area_root); /* address-sort this list */ tmp = rb_prev(&va->rb_node); if (tmp) { struct vmap_area *prev; prev = rb_entry(tmp, struct vmap_area, rb_node); list_add_rcu(&va->list, &prev->list); } else list_add_rcu(&va->list, &vmap_area_list); } As far as I can know map_area is a range for the vmalloc to alloc non-contigious memory, which confuses me is that why not use va->va_start > tmp_va->va_start and va->va_end < tmp_va->va_end to insert a new vmap_area. Can a virtual address mapping overlap? One more question In alloc_map_area, I found this part of code. /* from the starting point, walk areas until a suitable hole is found */ while (addr + size > first->va_start && addr + size <= vend) { if (addr + cached_hole_size < first->va_start) /* cached_hole_size */ cached_hole_size = first->va_start - addr; addr = ALIGN(first->va_end, align); if (addr + size < addr) goto overflow; if (list_is_last(&first->list, &vmap_area_list)) goto found; first = list_next_entry(first, list); } It seems like just inert a map_area at the end of list, what dose suitable hole means? Why not add this? if(addr+size < first->va_start) goto notound

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question re. kernel licenses
by Miles Fidelman Sept. 1, 2016

Sept. 1, 2016

Perhaps a silly question, but who actually holds the copyright on the kernel? I know it's released under the GPL, but, for the life of me, I can't find any statement of who is actually granting the licenses (i.e., who holds the copyright), and I can't seem to find any kind of copyright assignment statement that contributors are required to execute. So, how does this all work? Thanks! Miles Fidelman -- In theory, there is no difference between theory and practice. In practice, there is. .... Yogi Berra

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show image of current buffer in frame buffer (/dev/fbX)
by Ran Shalit Aug. 30, 2016

Aug. 30, 2016

Hello, Is it possible to display in some way the current content of frame buffer ? I have some issue that on rendering to /dev/fb2 with one application (psplash), it goes to the correct output, but using another application (qt) it always goes to /dev/fb2 (even if I static link /dev/fb0 to /dev/fb2). I thought that if I can display the content of frame buffer, it will help me understand what's going wrong. Regards, Ran

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Device Driver problem
by Gurpartap Singh Aug. 30, 2016

Aug. 30, 2016

I am using Quectel gsm module on Arm board from olimex. While attaching the Device via USB, dmesg shows following: *qmi_wwan 2-1:1.0: not on our whitelist - ignored* *what does it mean?*

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[PATCH] staging: ieee80211.h: Correct spelling of "FUNCION"
by Robert P. J. Day Aug. 28, 2016

Aug. 28, 2016

Signed-off-by: Robert P. J. Day <rpjday(a)crashcourse.ca> --- diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211.h b/drivers/staging/rtl8192u/ieee80211/ieee80211.h index 09e9499..e3b4e43 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211.h +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211.h @@ -1487,12 +1487,12 @@ typedef enum _RT_PS_MODE eFastPs // Fast power save mode. }RT_PS_MODE; -typedef enum _IPS_CALLBACK_FUNCION +typedef enum _IPS_CALLBACK_FUNCTION { IPS_CALLBACK_NONE = 0, IPS_CALLBACK_MGNT_LINK_REQUEST = 1, IPS_CALLBACK_JOIN_REQUEST = 2, -}IPS_CALLBACK_FUNCION; +}IPS_CALLBACK_FUNCTION; typedef enum _RT_JOIN_ACTION{ RT_JOIN_INFRA = 1, @@ -1526,7 +1526,7 @@ typedef struct _RT_POWER_SAVE_CONTROL { struct timer_list InactivePsTimer; // Return point for join action - IPS_CALLBACK_FUNCION ReturnPoint; + IPS_CALLBACK_FUNCTION ReturnPoint; // Recored Parameters for rescheduled JoinRequest bool bTmpBssDesc; -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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[PATCH] staging: Fix misspelling "dissconect"
by Robert P. J. Day Aug. 28, 2016

Aug. 28, 2016

Signed-off-by: Robert P. J. Day <rpjday(a)crashcourse.ca> --- diff --git a/drivers/staging/wilc1000/host_interface.c b/drivers/staging/wilc1000/host_interface.c index 0b1760c..de567bc 100644 --- a/drivers/staging/wilc1000/host_interface.c +++ b/drivers/staging/wilc1000/host_interface.c @@ -1189,7 +1189,7 @@ static s32 Handle_ConnectTimeout(struct wilc_vif *vif) result = wilc_send_config_pkt(vif, SET_CFG, &wid, 1, wilc_get_vif_idx(vif)); if (result) - netdev_err(vif->ndev, "Failed to send dissconect\n"); + netdev_err(vif->ndev, "Failed to send disconnect\n"); hif_drv->usr_conn_req.ssid_len = 0; kfree(hif_drv->usr_conn_req.ssid); @@ -1774,7 +1774,7 @@ static void Handle_Disconnect(struct wilc_vif *vif) wilc_get_vif_idx(vif)); if (result) { - netdev_err(vif->ndev, "Failed to send dissconect\n"); + netdev_err(vif->ndev, "Failed to send disconnect\n"); } else { struct disconnect_info strDisconnectNotifInfo; -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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[help] How to test kernel code that I wrote?
by Louie Lu Aug. 25, 2016

Aug. 25, 2016

Hi everyone, I'm now reading *Unreliable Guide To Locking* which came from kernelnewbies.org (https://kernelnewbies.org/Documents/Kernel-Docbooks) What I want to do is trying run the code that in this doc from 7.1 All In User Context. In my knowing for kernel programming, I'll need to compile the code to something like `main.ko` then insert into kernel space using `insmod`. Here is the GitHub that I'm doing PoC code: https://github.com/grapherd/unreliable_guide_to_locking My question is, Is my knowing right? and, how can I use the function in main.ko (e.g. cache_add). I'm using these function by test.ko, is that a normal way to use it? in this doc have mention, there have hardirq, softirq. How can I test it from these irq method? Thanks! Louie Lu.

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Minimum build config for boot messages
by Andre Schmidt Aug. 23, 2016

Aug. 23, 2016

Hello, what is the minimum config to build a linux kernel that just prints boot messages/errors? I was going through my old experiments/notes and found that we used to get kernel boot message with vanilla allnoconfig. make ARCH=x86_64 allnoconfig make all qemu-system-x86_64 -kernel arch/x86/boot/bzImage Those commands above used to be enough, but now the produced kernel doesn't print any messages on the qemu screen. With some trial-and-error i was able to track down this commit https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit… and if i add CONFIG_EMBEDDED=n to my KCONFIG_ALLCONFIG file, i can see kernel errors again. I didn't investigate further cause i don't really know what i'm doing, but do wonder: Can you reproduce this? Is this (now) expected behavior? (and it was luck before, to get kernel messages with vanilla allnoconfig) Do we (now) need some specific option to enable kernel messages with allnoconfig? (CONFIG_EMBEDDED=n sounds pretty generic and doesn't feel right) Am i doing it all wrong? :D Curiously, Andre Schmidt ps. i'm aware of defconfig, but i would like to experiment/learn from bottom-up, rather than top-down.

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Ask help for swiotlb feature
by Wei, Jiangang Aug. 23, 2016

Aug. 23, 2016

Hi guys, I'm interested in swiotlb feature. And spent several days to read the codes. But it's too difficult to understand, and no docs be found in Documentation/ . Is there any help docs, blog or website to explain the implementation of swiotlb or it's background knowledge? Thanks, wei

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