Quoting Stephen Boyd (2015-01-19 11:44:35) > On 01/19/2015 01:57 AM, Srinivas Kandagatla wrote: > > Some of the clks can be registered & unregistered before the clk related > > debugfs > > entries are initialized at late_initcall. In the unregister path checking > > for only > > dentry before clk_debug_init() would lead dangling pointers in the debug > > clk list, > > because the list is already populated in register path and the clk pointer > > freed in > > unregister path. > > The side effect of not removing it from the list is either a null pointer > > dereference or if lucky to boot the system, the number of clk entries in > > debugfs disappear. > > > > We could add more checks like if (inited && !clk->dentry) but just removing > > the check for dentry made more sense as debugfs_remove_recursive() seems to > > be > > safe with null pointers. This will ensure that the unregistering clk would > > be > > removed from the debug list in all the code paths. > > > > Without this patch kernel would crash with log: > > Unable to handle kernel NULL pointer dereference at virtual address 00000000 > > pgd = c0204000 > > [00000000] *pgd=00000000 > > Internal error: Oops: 5 [#1] SMP ARM > > Modules linked in: > > CPU: 1 PID: 1 Comm: swapper/0 Tainted: G B > > 3.19.0-rc3-00007-g412f9ba-dirty #840 > > Hardware name: Qualcomm (Flattened Device Tree) > > task: ed948000 ti: ed944000 task.ti: ed944000 > > PC is at strlen+0xc/0x40 > > LR is at __create_file+0x64/0x1dc > > pc : [<c04ee604>] lr : [<c049f1c4>] psr: 60000013 > > sp : ed945e40 ip : ed945e50 fp : ed945e4c > > r10: 00000000 r9 : c1006094 r8 : 00000000 > > r7 : 000041ed r6 : 00000000 r5 : ed4af998 r4 : c11b5e28 > > r3 : 00000000 r2 : ed945e38 r1 : a0000013 r0 : 00000000 > > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel > > Control: 10c5787d Table: 8020406a DAC: 00000015 > > Process swapper/0 (pid: 1, stack limit = 0xed944248) > > Stack: (0xed945e40 to 0xed946000) > > 5e40: ed945e7c ed945e50 c049f1c4 c04ee604 c0fc2fa4 00000000 ecb748c0 > > c11c2b80 > > 5e60: c0beec04 0000011c c0fc2fa4 00000000 ed945e94 ed945e80 c049f3e0 > > c049f16c > > 5e80: 00000000 00000000 ed945eac ed945e98 c08cbc50 c049f3c0 ecb748c0 > > c11c2b80 > > 5ea0: ed945ed4 ed945eb0 c0fc3080 c08cbc30 c0beec04 c107e1d8 ecdf0600 > > c107e1d8 > > 5ec0: c107e1d8 ecdf0600 ed945f54 ed945ed8 c0208ed4 c0fc2fb0 c026a784 > > c04ee628 > > 5ee0: ed945f0c ed945ef0 c0f5d600 c04ee604 c0f5d5ec ef7fcc7d c0b40ecc > > 0000011c > > 5f00: ed945f54 ed945f10 c026a994 c0f5d5f8 c04ecc00 00000007 ef7fcc95 > > 00000007 > > 5f20: c0e90744 c0dd0884 ed945f54 c106cde0 00000007 c117f8c0 0000011c > > c0f5d5ec > > 5f40: c1006094 c100609c ed945f94 ed945f58 c0f5de34 c0208e50 00000007 > > 00000007 > > 5f60: c0f5d5ec be9b5ae0 00000000 c117f8c0 c0af1680 00000000 00000000 > > 00000000 > > 5f80: 00000000 00000000 ed945fac ed945f98 c0af169c c0f5dd2c ed944000 > > 00000000 > > 5fa0: 00000000 ed945fb0 c020f298 c0af168c 00000000 00000000 00000000 > > 00000000 > > 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 > > 00000000 > > 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 ebcc6d33 > > bfffca73 > > [<c04ee604>] (strlen) from [<c049f1c4>] (__create_file+0x64/0x1dc) > > [<c049f1c4>] (__create_file) from [<c049f3e0>] > > (debugfs_create_dir+0x2c/0x34) > > [<c049f3e0>] (debugfs_create_dir) from [<c08cbc50>] > > (clk_debug_create_one+0x2c/0x16c) > > [<c08cbc50>] (clk_debug_create_one) from [<c0fc3080>] > > (clk_debug_init+0xdc/0x144) > > [<c0fc3080>] (clk_debug_init) from [<c0208ed4>] (do_one_initcall+0x90/0x1e0) > > [<c0208ed4>] (do_one_initcall) from [<c0f5de34>] > > (kernel_init_freeable+0x114/0x1e0) > > [<c0f5de34>] (kernel_init_freeable) from [<c0af169c>] > > (kernel_init+0x1c/0xfc) > > [<c0af169c>] (kernel_init) from [<c020f298>] (ret_from_fork+0x14/0x3c) > > Code: c0b40ecc e1a0c00d e92dd800 e24cb004 (e5d02000) > > ---[ end trace b940e45b5e25c1e7 ]--- > > > > Signed-off-by: Srinivas Kandagatla <srinivas.kandaga...@linaro.org> > > > > Reviewed-by: Stephen Boyd <sb...@codeaurora.org> > Fixes: 6314b6796e3c "clk: Don't hold prepare_lock across debugfs creation"
Applied to clk-next. Regards, Mike > > -- > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, > a Linux Foundation Collaborative Project > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
